Commissioning Switches, Medium & High Voltage

Engineering Encyclopedia Saudi Aramco DeskTop Standards

Commissioning Medium/High Voltage Switches

Note: The source of the technical material in this volume is the Professional Engineering Development Program (PEDP) of Engineering Services. Warning: The material contained in this document was developed for Saudi Aramco and is intended for the exclusive use of Saudi Aramco’s employees. Any material contained in this document which is not already in the public domain may not be copied, reproduced, sold, given, or disclosed to third parties, or otherwise used in whole, or in part, without the written permission of the Vice President, Engineering Services, Saudi Aramco.

Chapter : Electrical File Reference: EEX30211

For additional information on this subject, contact W.A. Roussel on 874-6160

Engineering Encyclopedia

Electrical Commissioning Medium/High Voltage Switches

Content

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INTRODUCTION................................................................................................................ 1 SAUDI ARAMCO REQUIREMENTS................................................................................. 2 Indoor-Type.............................................................................................................. 4 Outdoor-Type ........................................................................................................... 8 EVALUATING MEDIUM/HIGH VOLTAGE SWITCHES UPON RECEIPT....................11 Visual Inspection......................................................................................................11 Verification Against Specifications ...........................................................................11 Ratings and Nameplate Data .........................................................................12 EVALUATING MEDIUM/HIGH VOLTAGE SWITCH INSTALLATION AND TESTING............................................................................................................................14 Visual Inspection......................................................................................................15 Alignment .....................................................................................................15 Contacts .......................................................................................................16 Mechanism/Linkage ......................................................................................16 Three-Phase Contact Blades Make and Break Together ................................17 Physical Damage...........................................................................................17 Lubrication ...................................................................................................18 Cleanliness....................................................................................................18 Suitability .....................................................................................................19 Mechanical Inspections and Tests .............................................................................19 Open/Close Operation...................................................................................20 Arcing Horns Function..................................................................................20 Bolt Torque ..................................................................................................21 Contact Wipe................................................................................................22 Mechanical Locking of Contact Blades .........................................................22 Key Interlock System Operation ...................................................................23 Electrical Tests.........................................................................................................25 Contact Resistance........................................................................................25 Insulation Resistance.....................................................................................26 Saudi Aramco DeskTop Standards



Oil Dielectric ................................................................................................26 High Potential...............................................................................................27 SYSTEM PRE-OPERATIONAL CHECK-OUT .................................................................29 Point-to-Point Wiring Check ....................................................................................29 Subsystem Check-Out ..............................................................................................29 Interlocks .................................................................................................................29 SYSTEM OPERATIONAL TESTING................................................................................30 Source Feed Compatibility........................................................................................30 Complete System Functional Test.............................................................................30 WORK AID 1: REFERENCES FOR EVALUATING MEDIUM/HIGH VOLTAGE SWITCHES UPON RECEIPT ...............................................32 Medium and High Voltage Load Interrupting Switch applications Checklist..............38 WORK AID 2: REFERENCES FOR EVALUATING MOTOR VARIABLE SPEED DRIVE INSTALLATION AND TESTING ..................................39 Information, Formulas, and Tables for Use in Evaluating the Results of Insulation Resistance (Megger) Tests .......................................................42 AC or DC Hi Pot Tests ............................................................................................43 Information, Formulas, and Tables for Use in Evaluating the Results of Hi-Pot Tests.............................................................................................43 GLOSSARY........................................................................................................................48

Saudi Aramco DeskTop Standards



Table of Figures

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Figure 1: Disconnect Switch Use on Example Feeder Bus (Type CA Switchgear Arrangement) ......................................................................................... 3 Figure 2: S&C Model PMH-9 Pad-mounted Switch ................................................. 5 Figure 3: Three-Pole, Vertical, Motor-Operated, Loadbreak Disconnect Switch ....... 6 Figure 4: Cut-Away View of a Typical Arc Extinguishing Chamber .......................... 7 Figure 5: Typical, Single-Pole, Medium-Voltage Disconnect Switch......................... 9 Figure 6: Close-Up View of a Disconnect Switch Contact Assembly........................10 Figure 7: Example Application of Disconnect Switch Key Interlocks .......................24 Figure 10: Saudi Aramco Requirements forPad-Mounted Switchgear with Load-Interrupting Switches............................................................32 Figure 11: Voltages and Insulation Levels for Load Interrupting Switches (From ANSI C37.72 - 1987)..................................................................33 Figure 12: Load, Cable Charging, and Interrupting Current Ratings (From ANSI C37.72 - 1987)..................................................................33 Figure 13: Guidelines for the Application and Selection of Load Interrupting Switches.............................................................................34 Figure 14: Construction Requirements for Medium and High Voltage Switch Types.........................................................................................35 Figure 14: Construction Requirements for Medium and High Voltage Switch Types (Cont’d)...........................................................................36 Figure 15: Load Interrupting Switch Preferred Ratings (From C37.32-1990) ...........37 Figure 16: Saudi Aramco Pre-Commissioning form, P-001, Switches; High and Medium Voltage Air, Oil, and SF-6 ........................................40 Figure 16: Saudi Aramco Pre-Commissioning form, P-001, Switches; High and Medium Voltage Air, Oil, and SF-6 (Cont'd)...........................41 Figure 17: Recommended Megger Test Voltages.....................................................42 Figure 18: Bolt Torque Values for Bus Connections................................................42 Figure 19: Table of Hi Pot Test Values....................................................................43 Figure 20: Example of Hi-Pot Testing (Good and Bad Insulation) ...........................44 Figure 21: GI 2.710 Excerpt....................................................................................46 Figure 21: GI 2.710 Excerpt (Cont'd) ......................................................................47




INTRODUCTION Large process and process support equipment in industrial facilities requires electric power to function. The electric power that is required to run equipment is passed through generation, transmission, and distribution systems that route the electric power to the correct equipment at the proper voltage levels. Large, complicated, and costly switchgear, transformers, and circuit breakers provide electric power control, fault isolation, and protection capabilities. Because of the size and complexity of power distribution systems, it is not economically feasible to use switchgear and circuit breakers for every switching or isolation application. Additionally, some switching applications do not require the capabilities and features that switchgear and circuit breakers provide. Medium and high voltage switches provide an inexpensive alternative to switchgear and circuit breakers. The selection of the type and size of the medium and high voltage switches that are used in Saudi Aramco is based on the technical, the installation, and the economic requirements of a facility. Facility switch technical requirements include the system voltage level and the normal and transient current levels for the electric power system. Once the switch for a given installation is selected, the switch and the support equipment (e.g., mounting platform and termination bushings) is ordered from the manufacturer, and it is then installed. The commissioning process for medium and high voltage switches in Saudi Aramco facilities is a process that ensures that a safe and cost-effective system is installed that performs to the specifications of the facility for the projected operating lifetime of the facility. Experience has shown that the time and the effort that is expended upfront to ensure safety, quality control, and adherence to Saudi Aramco and industry standards minimizes subsequent equipment failure. The medium and high voltage switch commissioning process involves inspections, verifications, and checks that determine whether the switch specifications and installation requirements are met. Tests are also performed that determine whether the electric power distribution system will operate properly and safely once the switch is installed. When a medium or high voltage switch is inspected and tested satisfactorily during the commissioning process, the system should operate in accordance with manufacturer's specifications for its maximum useful life. This Module provides information on the following topics that are pertinent to commissioning medium and high voltage switches for Saudi Aramco installations: • Saudi Aramco Requirements • Evaluating Medium/High Voltage Switches Upon Receipt • Evaluating Medium/High Voltage Switch Installation and Testing • System Pre-Operational Check-Out • System Operational Testing Saudi Aramco DeskTop Standards

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SAUDI ARAMCO REQUIREMENTS The basic operational function of a switch is to isolate power from a source to a load; however, with modifications or changes in construction, switches can have several different functions and can be used to serve many purposes. Disconnect switches can be used to alter circuit arrangements and to provide electrical isolation for equipment that has to be removed from service for maintenance. Standard disconnect switches are designed to be opened and closed to isolate a single load or group of loads when no current flow is present. A good example of the relationship between a standard disconnect switch and a circuit breaker is shown in Figure 1. Figure 1 shows a standard distribution bus that is fed by one generator. Each feeder has a circuit breaker and a disconnect switch. This type of bus configuration should only be used where interruptions to load service are unimportant because outages must exist to all feeders simultaneously when the feeder bus, the generator breaker, or the generator is out of service for any reason. The circuit breaker provides protection against short circuits on the feeder and enables the feeder to be removed from service, if necessary, while it is carrying load. With the breaker open, the disconnect switch serves as additional backup protection for personnel during maintenance or repair work on the feeder. The disconnect switch also enables the feeder breaker to be isolated from the bus for inspection and maintenance on the breaker. Disconnect switches are frequently arranged so that when the disconnect switch blades are opened, they are connected to a grounded clip to prevent maintenance personnel from exposure to dangerous voltage potentials. The example that is shown in Figure 1 is of the Westinghouse type CA switchgear, which utilize isolator switches in the configuration that is shown. This equipment is non-standard and will not be used in future projects.


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Figure 1: Disconnect Switch Use on Example Feeder Bus (Type CA Switchgear Arrangement)

With certain modifications, switches can also be used to isolate circuits under load. Switches that have the capability to interrupt load current are commonly called loadbreak switches. Depending upon the installation requirements, switches can also be fused or unfused. Fused switches provide additional protection and coordination capabilities that enhance the versatility of switch application.


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In addition to isolating a single load or group of loads, switches can be used to transfer power to a load from one source to another. The ability to transfer loads from a primary source of power to an alternate source of power provides increased system reliability and continuity of power. Switches can also be used in a complex power distribution scheme that requires sectionalizing or the multiple tapping of a primary feeder to serve transformers or laterals. In addition, special application switches are available that can intentionally ground circuits, provide power from standby systems, or serve as a temporary circuit breaker replacement. Special application switches are not covered in this Module. The requirements for switches that are used for Saudi Aramco installations are found in SAES-P-116, Switchgear and Control Equipment, 16-SAMSS-510, Load Interrupting Switches 0.6 kV through 38 kV, and related industry standards. The standard that is used as the base reference for 16-SAMSS-510 is the Pad-Mounted Switchgear and Load Interrupting Switches section of IEEE C37. The IEEE C37 standard is a compilation of guides and standards that are used for circuit breakers, switchgear, relays, substations, and fuses. Switches use either air, oil, or SF6 gas as the insulating (or interrupting) medium. The most common types of switches that are used in Saudi Aramco installations are the air break switches and oil-filled switches; however, because of industry advances in SF6 interruption technology, the current trend is to replace oil-filled-type switches with SF6 types. Although many switches are available for power distribution applications, Saudi Aramco installations usually use the following manufacturers' switches: • ABB (SF6-type) RGC • G&W GRAM (oil-type) • S&C PMH-9-11-6 (oil-type) • Westinghouse WLI air break • GE air break The two general types of switches that are found in Saudi Aramco installations are the indoor-type and the outdoor-type. Depending on whether the switch is used indoors or outdoors, the physical construction of a switch may be different, but the basic operational functions of the switch will remain the same. Indoor-Type Indoor-type switches are used in indoor power distribution systems in switchgear. Saudi Aramco commonly uses ABB-SF6 type switches. Westinghouse switches are generally used indoors as isolation switches.


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Pad-mounted switchgear is an assembly in which all energized parts are insulated and completely enclosed within a system that is grounded and shielded. Pad-mounted switchgear should use an enclosure that is suitable for the environment and that utilize tamper-resistant construction for outdoor above-ground installation. Figure 2 shows a one-line diagram of an S&C Model PMH-9 pad-mounted switch. The PMH-9 is a fused switch that is commonly used in Saudi Aramco installations because it provides a primary-selective service. With primary-selective service, one circuit serves as the preferred power source for the load. The second power source remains available as the alternate source of supply. If the preferred source fails, switching operations are performed to provide power to the load from the alternate source. In Figure 2, the S&C Model PMH-9 pad-mounted switch is being used to switch and protect three-phase transformer #1 and three-phase transformer #2. The transformers can be switched at the load (fused) side of the switch, and the loads can be selectively served from either of the two power sources. Reference is made to the PMH-9 as an example of the switches currently used in Saudi Aramco; however, the PMH-9 and other oil switches are being replaced.

Figure 2: S&C Model PMH-9 Pad-mounted Switch Saudi Aramco DeskTop Standards

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Figure 3 shows a typical, indoor-type, high voltage disconnect switch. The disconnect switch that is shown in Figure 3 is a three-pole, vertical, motor-operated, loadbreak disconnect switch. The function of the movable switch's operating blade is to make contact with the contact assembly and to provide a path for system current. The function of the arc extinction chamber is to suppress and dissipate any arc that forms when the switch is opened. The operating bar and the spring assembly function together to control the movement of the movable operating blade, the arcing pin, the arcing pin cantilever, and the blade operating link for each of the switch phases. The function of the terminals is to provide a connection point between the line and the load side of the switch and the rest of the electrical system. The mounting insulators function to provide structural support and insulation to ground.

Figure 3: Three-Pole, Vertical, Motor-Operated, Loadbreak Disconnect Switch


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The disconnect switch is opened by means of the operating mechanism, which, with the assistance of the spring assembly, rotates the operating bar about its axis. As the operating bar rotates, each blade's operating link acts to open its respective movable operating blade. As the contacts in the main contact assemblies part, the arc extinguishing chamber suppresses and dissipates any arc that is formed. The arc extinguishing chamber in the example high voltage switch is an extra feature of the particular switch that is shown. Figure 4 shows a cut-away operational view of a typical arc extinguishing chamber. Part A of Figure 4 shows that as the arcing pin moves away from the stationary arcing contact during a disconnect switch opening operation, an arc is formed. Part B of Figure 4 shows that when the arcing pin slides from between the plates, the plates are forced against the arc. As the arcing pin clears the opening, the gas that is created in the arcing process is forced through the opening into the expansion chamber, and the arc is extinguished.

Figure 4: Cut-Away View of a Typical Arc Extinguishing Chamber


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Outdoor-Type Outdoor-type switches are used in outdoor power sections of transmission or distribution systems. Outdoor-type switches are usually pad-mounted air-interrupting switches. Pad-mounted outdoor-type switches are an assembly in which all energized parts are insulated and grounded; however, all major components of the switch (e.g., blades and insulating supports) are exposed. For outdoor-type switches, Saudi Aramco commonly uses G&W switches. SGC-type fuse disconnect switches are generally used outdoors to meet isolation requirements. Figure 5 shows a typical outdoor-type, single-pole, medium-voltage disconnect switch. The switch that is shown in Figure 5 is a vertical-break, outdoor air switch that is designed for operation by either a manual or a motor operating mechanism. The spring assembly and the hinge tie function together to position the main blade. The upper crank arm, the expansion link assembly, and the lower bearing assembly function together to rotate the main blade about its axis to lock and unlock the main blade contact assembly. The stationary arc horn and the movable arc horn function to dissipate the arc that is produced when the switch is operated. The three insulation stacks function to provide structural support and insulation to ground. The disconnect switch is opened by means of the operating mechanism, which rotates the left-most insulation stack of the disconnect switch that is shown in Figure 5. As the left-most insulation stack rotates, the upper crank arm and the expansion link assembly act to rotate the main blade about its axis. As the main blade rotates, the movable contact surfaces also rotate, and they disengage from the contact assembly. As the left-most insulation stack continues to rotate, the upper crank arm and the expansion link assembly lift the main blade into the open position with the assistance of the spring assembly.


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Figure 5: Typical, Single-Pole, Medium-Voltage Disconnect Switch


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Figure 6 shows a close-up view of a typical, outdoor-type, single-pole, medium-voltage disconnect switch contact assembly. In Figure 6, the main blade is shown in a partially open position. The contacts in the contact assembly are spring-loaded so that, when the switch is closed and when the main blade's movable contact surfaces are horizontal, the main blade is locked in place. As the switch opens, the movable arc horn and the stationary arc horn control and dissipate any arc that is formed.

Figure 6: Close-Up View of a Disconnect Switch Contact Assembly


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EVALUATING MEDIUM/HIGH VOLTAGE SWITCHES UPON RECEIPT Because disconnect switches that are chosen for a particular installation must provide the proper operation, protection, and maintenance capabilities, they are verified to ensure that they comply with Saudi Aramco and industry standards and practices. The minimum mandatory requirements for the design and construction of disconnect switches are provided in Work Aid 1. The installation of a medium or high voltage switch is a process that takes place over a period of time. The installation begins with an identified need for a switch installation (e.g., a new facility). Because power is necessary for critical loads at the new facility, a switch installation is designed. After the design is approved, the switch and the switch equipment (e.g., enclosures or switchgear) are ordered from the manufacturer. Once the switch is received from the manufacturer, it must be evaluated to ensure that it is proper for the installation. The purpose of the evaluation is to verify that the correct switch was received from the manufacturer and that the proper installation specifications and parameters are met. This section describes how medium and high voltage switches are evaluated upon receipt. Visual Inspection When a medium or high voltage switch is received from the manufacturer, a visual inspection must be performed. The purpose of the visual inspection is to verify that the switch that was received from the manufacturer is in good physical condition and that all of the requested parts and accessories are present. Because of the damage that can occur to the moving parts that are associated with switches during installation, a cursory inspection is performed at the receiving point. During the cursory inspection, the inspection personnel look for obvious equipment damage and determine whether the necessary support equipment (e.g., manual operators and technical manuals) are present. A detailed inspection of the switch is performed when it is completely installed at the site or facility. Verification Against Specifications When a new facility or facility modification is at the equipment installation stage, the design of the installation has already been completed. The type of switch that is selected for a specific power system should be shown in the drawings, the prints, or the specifications for the installation. The purpose of verifying the switch against the specifications is to ensure that the equipment that is being installed meets Saudi Aramco and industry standards.


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Generally, the verification against specifications consists of a determination of whether the type and rating of the equipment that is to be installed match the size and the type of the equipment that is required for the installation. In some cases, this determination is accomplished by reading an electrical plan that identifies the switch size and type. The Electrical Engineer inspects the manufacturer's nameplate data on the switch and compares it to the requirements on the electrical plan to determine whether the correct equipment is being used. In other situations, the Electrical Engineer must rely on his knowledge of the correct application of automatic transfer switch sizes and types to determine whether the correct equipment is being used. Any data sheets or manufacturer information that were used to order the switchgear from the manufacturer must also be consulted. Any quality control, quality assurance, and test data that are provided with the automatic transfer switch must also be reviewed. Ratings and Nameplate Data All pad-mounted switchgear that contain load interrupting switches that are used in Saudi Aramco power systems should have a nameplate that is clearly visible on the front of the unit. The nameplate should contain manufacturer and rating information. In accordance with ANSI C37.72, the manufacturer and the rating information that should appear on the nameplate of padmounted switchgear with load interrupting switches must include the rated frequency, the rated maximum voltage, the rated dielectric strength, and the current ratings. Frequency Rating - Switches and electric power distribution systems are designed to operate at a specific frequency. Saudi Aramco electrical distribution systems are designed to operate at 60 Hz. Rated Maximum Voltage - Medium and high voltage switches are designed for and should be marked with the rated maximum voltage. The rated maximum voltage is the highest rms voltage above nominal system voltage for which the switch is designed, and it is the upper limit for operation. Voltage rating information is provided in Work Aid 1. Rated Dielectric Strength - To test a switch to determine whether the dielectric strength (insulation level) is adequate to protect the switch against damage from lightning and other surges, the switch is impulse-tested. The basic impulse insulation level (BIL) is the reference impulse level, expressed in full wave kilovolts, that the switch can withstand without a flashover. The BIL is based on a test that uses a wave that is intended to simulate a lightning stroke. The wave that is used for the test that is performed on a switch is a 1.2 x 50 microsecond wave. The wave goes from zero to a crest voltage in 1.2 microseconds, and the wave reaches a magnitude that is half of the value of the crest voltage in 50 microseconds. In the tests, both positive and negative impulse voltages are applied to the switch without damage or flashover. The wave crest value is equal to the rated full wave impulse withstand voltage of the switch.


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A low-frequency withstand voltage test is also performed on pad-mounted switchgear that contain load interrupting switches. The low-frequency withstand voltage test determines the ability to withstand a low frequency voltage for a period of time without flashover or damage to equipment (e.g., bushings). Current Ratings - Pad-mounted switchgear that contain load interrupting switches are designed for and should be marked with the continuous current that the switch is capable of carrying and the fault current values that the switch is capable of interrupting, without damage to the switch. Specific current ratings are as follows: • Rated Continuous Current. The rated continuous current is the amount of current that the switch can continuously carry without exceeding the allowable temperature rise. • Load Interrupting Current. The load interrupting current is the highest value of the load current that the switch can interrupt without damage from flashover and without exceeding the allowable temperature rise. • Short Time Currents. The short time currents are the highest values of momentary, making, and one-second currents that the switch can interrupt without damage from flashover and without exceeding the allowable temperature rise. • Magnetizing and Cable Charging Currents. The magnetizing and cable charging currents are interrupting currents that the switch can withstand without damage from flashover and without exceeding the allowable temperature rise.


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EVALUATING MEDIUM/HIGH VOLTAGE SWITCH INSTALLATION AND TESTING The process to determine whether medium and high voltage switches should be commissioned is to verify that all the inspections and tests have been performed properly and to verify that the test results are within the specifications that are designated by the applicable Saudi Aramco and industry standards. Installation inspections are performed to verify that proper medium and high voltage switch installation materials are used, that installation specifications and parameters are met, and that proper installation procedures are followed. The installation inspection is conducted to ensure that medium and high voltage switches and associated switchgear will function properly once they are installed. Electrical tests are performed to check the ability of medium and high voltage switches and any associated support equipment to function under all operating conditions and loads. Installation tests should detect shipping or installation damage, gross manufacturing defects, or errors in workmanship or installation. The Saudi Aramco Pre-Commissioning Form, P-021, SF-6 Pad-Mounted Enclosure, contains guidance on the items that should be inspected, checked, and tested during the commissioning process. A failure in any one of the many inspections, checks, or tests that are performed on medium and high voltage switches during the commissioning process is sufficient to prevent the equipment from being commissioned. Because of the different inspection items that are associated with switches, several courses of action are available for switches that have failed a visual inspection. The course of action depends on the part of the switch that failed the visual inspection. Some switch parts (e.g., insulation support stacks) can be corrected through the replacement of the parts that failed the visual inspection. Visual alignment, mechanism/linkage, lubrication, or cleanliness inspection failures can usually be corrected through maintenance procedures. A visual physical damage and suitability inspection failure will probably require the replacement of the entire incorrect or damaged part. For mechanical test and inspection failures, different courses of action may be required. For example, a bolt torque test failure can be corrected through adjustment of the bolts with a torque wrench. Because an electrical inspection or test failure can be caused by a construction error, equipment age, or operational misuse, some type of troubleshooting or maintenance activity should be performed on the switch when an electrical inspection or test is failed. Some electrical inspection or test failures are not repairable, and such failed equipment must be replaced. A failure in any one of the many tests that are performed on a switch during initial installation and commissioning, no matter how insignificant the test may seem, is sufficient cause not to allow the switch to be placed in service. The inspector must be able to determine the appropriate action to take to commission the switch.


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The proper evaluation of inspection and testing data during the commissioning process can maximize the operating time of equipment installations through a determination of trends towards failure. Failure prediction can drastically reduce equipment downtime. If a failure is predicted, operational changes can be made, maintenance can be performed, or equipment that is failing can be replaced in a controlled manner. If a problem is corrected before it causes damage, operating costs will be lower because a malfunction will be prevented. Malfunctions can cause associated (or nearby) equipment damage, disruption of service, or the activation of emergency repair crews. Visual Inspection Visual inspections are used to assess the physical condition of medium and high voltage switches. A visual inspection is a pass/fail verification about a particular aspect of either the physical condition or the operation of medium and high voltage switches. P-001 contains guidance on the items that should be checked during a visual inspection of medium and high voltage switches. Because the criteria that are established to determine the acceptability of the visual inspections can be subjective, the visual inspections should be performed by an experienced Electrical Engineer. The following visual inspections are used to assess the condition of medium and high voltage switches in Saudi Aramco systems: • Alignment • Contacts • Mechanism/Linkage • Three-Phase Contact Blades Make and Break Together • Physical Damage • Lubrication • Cleanliness • Suitability Alignment The purpose of the alignment inspection is to ensure that the medium voltage or high voltage switch will properly pass current when it is connected to the rest of the electrical system and that no improper connections are present. Improper alignment can cause uneven equipment heating and wear. Proper alignment of the live disconnect parts (i.e., disconnect switch jaws, blades, and connectors) ensures a proper electrical connection and minimizes adverse heating effects. Due to the construction of switches, most of the parts are visible to inspection personnel, and the proper switch alignment, connections, and clearances will be evident.


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The alignment visual inspection should be performed during the normal maintenance cycle of switchgear and medium and high voltage switches as determined by Saudi Aramco procedures and practices. Technical data to evaluate the results of the alignment inspection can be found in the switchgear and switch manufacturer's technical manuals. Contacts When a medium or high voltage switch is connected to the electrical system and is closed, the contacts provide a current path through the switch. The contacts must also withstand current levels that occur when the switches are opened under load. Damage can occur at the contacts as a result of the mechanical stress from closing operations and from the electrical arc that forms during contact opening operations. The purpose of the visual inspection of the contacts is to ensure that they provide a low resistance current path and that the contacts of medium and high voltage switches can safely interrupt load current and can be closed under load. Small burn and pock marks can develop on the surface of the contacts over the operating life of a switch. Such marks will not interfere with the operation of the contacts, but the contacts will need to be replaced when they erode over time to some wear point that is defined by the manufacturer. For medium and high voltage switches that have arc extinction chambers (e.g., air, oil, or vacuum), a contact wear indicator is checked. The visual inspection of the switch contacts should be performed during the normal switchgear or switch maintenance cycle as determined by Saudi Aramco procedures and practices. The most stringent of the applicable maintenance cycles is the cycle that should be applied. Technical data to evaluate the results of the contact visual inspection can be found in the switchgear or switch manufacturer's technical manual. Mechanism/Linkage The mechanism/linkage assembly of medium and high voltage switches performs the actual movement of the switch contacts during open or close operations. The purpose of the mechanism/linkage inspection is to ensure that the mechanism/linkage can move freely. Free movement of the mechanism/linkage will ensure that the switch can be properly operated by the operator (or operating mechanism). The inspector should visually determine that no obstructions exist that will restrict or impede the proper operation of the mechanism/linkage. The mechanism/linkage visual inspection should be performed during the normal maintenance cycle of switchgear and switches as determined by Saudi Aramco procedures and practices. The most stringent of the applicable maintenance cycles is the cycle that should be applied. Technical data to evaluate the results of the mechanism/linkage visual inspection can be found in the switchgear and switch manufacturer's technical manuals.


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Three-Phase Contact Blades Make and Break Together When three-phase medium or high voltage switches operate, the contacts must open and close as a group. Additionally, the arcing contacts (and the arc horn, if used) must make and break in sequence with the main movable blade contacts during switch operations. The proper contact make and break should be observed during the open/close operation test. Proper contact make and break consists of both the physical contact operation and the sequence of the contact operation. The three-phase contact blades' make and break visual inspection should be performed during the normal maintenance cycle of the switches as determined by Saudi Aramco procedures and practices. The most stringent of the applicable maintenance cycles is the cycle that should be applied. Technical data to evaluate the results of the three-phase contact blades' make and break visual inspection can be found in the switch manufacturer's technical manual. Physical Damage Physical damage of switches can prevent the proper operation of protective equipment (e.g., arc horn failure), or it can lead to dangerous system grounds or shorts. Because of the magnitude of the electric energy that passes through medium or high voltage switches and the installed interrupting devices and because of the large forces that are required to open and close switches, any physical damage to switches can propagate and will often require major equipment replacement. The most obvious and common forms of physical damage are cracks, dents, and missing or broken pieces. The switch blades should be checked for warps, distortions, or bent structural framework. The purpose of the physical damage inspection is to identify whether corrective maintenance or equipment replacement is necessary due to physical damage. The physical damage inspection of the medium or high voltage switch must include any and all equipment that is contained or attached to the switch. Medium and high voltage switches (and the support equipment) that show any form of physical damage, no matter how small, should be determined to have failed the physical damage inspection. The physical damage visual inspection should be performed during the normal maintenance cycle of switchgear and switches as determined by Saudi Aramco procedures and industry practices. The most stringent of the applicable maintenance cycles is the cycle that should be applied. Technical data to evaluate the results of the physical damage visual inspection can be found in the switchgear and switch manufacturer's technical manuals.


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Lubrication The lubrication visual inspection should be performed in conjunction with the mechanism/linkage visual inspection. The purpose of the lubrication visual inspection is to ensure that all moving parts, bearing points, and sliding mechanisms of the medium or high voltage switch are properly lubricated and free of rust. Before the application of new lubrication can take place, hardened grease, dirt, and rust should be removed from the surfaces that require lubrication. A cloth that is dampened with kerosene should be used to remove the hardened grease and dirt. Care must be taken to ensure that the cloth does not deposit fibers on the moving parts. The deposit of cloth fibers on moving parts can cause subsequent improper mechanism operation. After the proper preparation of the moving parts, a thin layer of lubrication should be applied. Excess lubrication should be wiped off with a clean cloth. The lubrication visual inspection should be performed during the normal maintenance cycle of switchgear and switches as determined by Saudi Aramco procedures and industry standards. The most stringent of the applicable maintenance cycles is the cycle that should be applied. Lubrication of the switches is acceptable if it allows free range of motion of the switch parts and if the lubrication is not hard. Technical data to evaluate the results of the lubrication visual inspection can be found in the switchgear and switch manufacturer's technical manuals. Cleanliness The purpose of the cleanliness visual inspection is to ensure the proper operation of the medium or high voltage switch over the maximum operating life. The accumulation of dirt (over a period of time) in a switch will impede the proper operation of the switch and the installed protective equipment, and the accumulation of dirt will reduce the dielectric strength of the insulation stacks and mountings. To maintain the proper operation of the switch, the accumulation of heavy amounts of dust should be cleaned away from the switch during maintenance cycles. Inspections should be performed both before and after cleaning or dust removal is conducted. For switches that are installed in switchgear or enclosures, telltale signs can be left in dust that can reveal otherwise hidden adverse conditions. For example, moisture droplets can leave small craters in dust. Dust can also mask adverse conditions. For example, a carbon track that exists on a bus support may be completely hidden under a layer of dust.


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The cleanliness visual inspection should be performed during the normal maintenance cycle of switchgear and switches as determined by Saudi Aramco procedures and industry practices. The most stringent of the applicable maintenance cycles is the cycle that should be applied. Switches that are installed in extremely dirty, dusty, or humid areas may have to be cleaned more often than once during the normal maintenance cycle. Dirt or dust should be cleaned away when, in the opinion of the person who performs the maintenance, the dirt or dust would impede the switch operation. Suitability The purpose of the suitability visual inspection is to determine whether the medium or high voltage switch is appropriate for the application in which it is placed. To determine the suitability of a switch, a visual inspection of the nameplate information on the switch should be performed and compared to the known information about the electrical system in which the switch is placed. If the nameplate information does not match the ratings of the electrical system, the switch should be replaced. Although the suitability inspection of the switch is usually performed during commissioning, it should also be performed during the normal maintenance cycle of the switch as determined by Saudi Aramco procedures and industry standards. Periodic visual inspections should be performed to ensure that changes that may have been made to the system have not exceeded the ratings of the disconnect switch. The most stringent of the applicable maintenance cycles is the cycle that should be applied. Technical data to evaluate the results of the suitability visual inspection can be found in Saudi Aramco and industry standards as well as in the switch manufacturer's technical manual. Mechanical Inspections and Tests Mechanical inspections and tests are used to assess the ability of a medium or a high voltage switch to physically perform the mechanical movements that are necessary to make or to break an electric circuit. The mechanical inspections and tests also assess the safety functions (e.g., key interlock) of the switch. The mechanical inspections and tests that are performed on medium and high voltage switches that are installed in Saudi Aramco systems are as follows: • Open/Close Operation • Arcing Horns Function • Bolt Torque • Contact Wipe • Mechanical Locking of Contact Blades • Key Interlock System Operation


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Open/Close Operation Some medium or high voltage switches in Saudi Aramco electrical systems can go from maintenance cycle to maintenance cycle without a single operation. A switch must always be in a condition to operate, no matter how infrequently the switch has been used. The purpose of the open/close operation test is to ensure that the switch opens and closes properly. To perform the open/close operation test, the switch is cycled from the fully open position to the fully closed position and back to the fully open position. During the closing and opening operations, the mechanical condition of all of the connected devices (e.g., arc horns and position indicators) is checked for proper operation. For medium or high voltage switches with interruption chambers in which the contacts are not visible, the manufacturer's technical manual should contain information on the minimum moving contact travel distances. The open/close operation test should be performed during the normal maintenance cycle of a medium or high voltage switch as determined by Saudi Aramco procedures and practices. The most stringent of the applicable maintenance cycles is the cycle that should be applied. Technical data to evaluate the results of the open/close operation test can be found in the switch manufacturer's technical manual. Arcing Horns Function Medium and high voltage switches can contain arc horns, arc chutes, arcing tips, arcing boxes, or a combination of all of these arc-suppression devices. The arc horns direct developed arcs away from the switch contact assembly, which prevents damage to any connected or adjacent equipment. The purpose of the visual inspection of the arc horns (and other arc-suppression devices) is to ensure that the arc horns can safely suppress the arc that forms when the switch opens. The arc horns (or arcing tips) should be adjusted so that the arcing devices close before the main contacts close and open after the main contacts open. During the visual inspection, the arc horns (or arcing tips) should be inspected for pitting or scoring that could prevent the arc horn from properly directing the developed arc. If the medium or high voltage switch uses an arc chute or an arc extinguishing chamber, the chute or chamber should be inspected for burn marks, scale, and cracks. Burn marks change the consistency of the surface of an arc chute. If burn marks are present on an arc chute, the arc chute should be replaced. Scale is the accumulation of foreign material in the arc chutes that can impede the ability of the arc chutes to extinguish an arc. Scale should not be removed from the surface of the arc chutes; so, the inspector must determine whether the scale will impede the ability of the arc chute to extinguish an arc. If the inspector determines that the scale will impede the ability of the arc chute to extinguish an arc, the arc chute is replaced. Cracks form in the arc chutes during the normal operation of a switch. The inspector must determine whether the cracks will interfere with the ability of the arc chute to extinguish an arc, and he should replace the arc chute accordingly. Saudi Aramco DeskTop Standards

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Oil-filled switches are also used for medium and high voltage switch applications. Oil-filled medium and high voltage loadbreak switches are commonly used by Saudi Aramco for industrial applications. Oil-filled switches are only suitable for outdoor use. For high making and breaking capacity, the oil-filled switch should incorporate either a spring toggle mechanism or some form of arc control. The preferred type of switch construction has spring toggle mechanisms that are enclosed inside the tank. Regular inspection and maintenance of oil-filled switches are necessary to remove accumulated sludge and to test the quality of the oil. The visual inspection of the arc suppression device (e.g., the arc horn) should be performed during the normal maintenance cycle of a switch as determined by Saudi Aramco procedures and practices. The most stringent of the applicable maintenance cycles is the cycle that should be applied. Technical data to evaluate the results of the arc suppression device visual inspection can be found in the switch manufacturer's technical manual. Bolt Torque The terminations of most medium and high voltage switches use bolted connections. Medium and high voltage switch supports and movable blades use bolted metal segments. For a given switch installation, many connecting bolts must be installed. Each bolt has a torque specification that should be met for the installation. During the evaluation of the switch installation, the Electrical Engineer should spot test the torque on the connecting bolts. When the spot test of the connecting bolts is performed, the Electrical Engineer should check that all bolted connections have the correct hardware (e.g., washers and nuts) installed. The purpose of a bolt torque inspection is to ensure that enough force is present to hold the bolts in place during all required operations. To determine the amount of force that exists at a bolt, a torque wrench is applied to the bolt in the direction that will tighten the bolt, and the amount of torque is read. The bolt torque inspection should be performed during the normal maintenance cycle of medium and high voltage switches as determined by Saudi Aramco procedures and industry practices. The most stringent of the applicable maintenance cycles is the cycle that should be applied. Technical data to evaluate the results of the bolt torque inspection can be found in the Saudi Aramco Pre-Commissioning Form, P-000, Testing Guidelines, as well as the switch manufacturer's technical manual. Bolt torque values are provided in Work Aid 2.


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Contact Wipe The purpose of the mechanical inspection of the contact wipe is to ensure that the correct contact wipe is present at the switch contacts. The contact wipe should be observed and measured during the open/close operation test of switches. The contact wipe is the distance that the stationary contacts move as the switch main contact blade moves from the open to the closed position. All various switch main contact assembly designs require that specific pressures be kept on the movable blade contacts to ensure proper electrical contact. The contact pressure is usually a function of the travel distance of the stationary contacts after the tips touch during a closing operation. The contact wipe inspection should be performed during the normal maintenance cycle of a switch as determined by Saudi Aramco procedures and practices. The most stringent of the applicable maintenance cycles is the cycle that should be applied. Technical data to evaluate the results of the contact wipe inspection measurements can be found in the switch manufacturer's technical manual. Mechanical Locking of Contact Blades If the medium or high voltage switches are provided with a locking feature, a mechanical inspection and test should be performed on the mechanical locking jaws of switches. The purpose of the mechanical inspection and test of the mechanical locking feature of a switch blade is to ensure that the blade contact locks into place when the switch is closed and to test that the locking feature releases the blade when the switch is opened. The inspection and test of the mechanical locking feature is performed by cycling the switch and by observing the proper operation of the locking feature. For gang-operated switches, the inspection and test personnel should also determine that each phase makes connection and that the locking jaws lock simultaneously. The mechanical inspection and test should be performed on the mechanical locking feature during the normal maintenance cycle of a switch as determined by Saudi Aramco procedures and practices. The most stringent of the applicable maintenance cycles is the cycle that should be applied. Technical data to evaluate the results of the mechanical locking feature inspection and test can be found in the switch manufacturer's technical manual.


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Key Interlock System Operation Disconnect switches are usually associated with a circuit breaker or switchgear installation. When a disconnect switch is in series with or associated with a circuit breaker, an interlock should be used to prevent the opening of the disconnect switch with the breaker closed. The interlock can take the form of mechanical linkages, electrical relaying systems, or key interlocks. Key interlocks are an inexpensive way to prevent the inadvertent operation of disconnect switches. Figure 7 shows an example application of loadbreak switches in a high voltage system with key interlocks. In Figure 7, the loadbreak switches are used to sectionalize loads between two alternative feeders in a loop network. The "X" sectionalizing loadbreak switches provide operational and load division switching. It is normal to operate such a system with one end open, in which case a fault will be cleared by the operation of one of the "Y" breakers. The faulty section can then be isolated, and the supply can be restored to the rest of the system. Key interlocks (Kirk-Key) may be used on manually operated schemes to prevent inadvertent paralleling of the two different supply feeders (i.e., the preferred and the emergency supply). For both the "X" and "Y" switches, one set of keys is available for each switch pair. Because only one key is provided for each pair, only one of the two switches in each pair can be closed at any one time.


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Figure 7: Example Application of Disconnect Switch Key Interlocks

Switches that use key interlocks may be in parallel, or they may be associated with parallel power sources. Because a switch with a key interlock can only be operated when the key is inserted, and because only one key is provided for each pair of switches, both switches cannot be operated at the same time. If both switches cannot be operated simultaneously, the inadvertent paralleling of power sources is physically impossible. The removal of the key can render both switches inoperable during troubleshooting or maintenance evolutions.


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The purpose of the mechanical operation inspection is to ensure that the key interlock system will function properly. The basic method that is used to perform this inspection is to attempt to operate both switches at the same time. Extreme caution must be exercised when this test is performed. The entire system should be deenergized prior to the test to prevent serious injury to personnel or damage to equipment in the event that the interlock does not function properly. The results of the key interlock system mechanical operation inspection are satisfactory if the interlock system is visually observed to properly operate. Electrical Tests Electrical tests are performed to check the ability of switches to operate for a reasonable future period of time under all operating conditions and loads. Acceptance or installation tests will usually detect shipping or installation damage and gross defects or errors in workmanship in switch construction. Maintenance tests are performed at periodic intervals during the operating life of a switch. The following electrical tests are performed on Saudi Aramco switches: • Contact Resistance • Insulation Resistance • Oil Dielectric • High Potential Contact Resistance The purpose of the contact resistance test of a medium or high voltage switch is to identify contacts that are defective or detrimental to the operation of the switch. The contact resistance test may also identify loose connections in a switch. With the system deenergized and isolated, the leads of a digital, low-resistance ohmmeter should be placed across line and load sides of the switch blade, and measurements should be taken across the contacts of each phase. A digital, low-resistance ohmmeter can deliver enough power to the switch to make accurate readings that have more validity than those readings that can be obtained through the use of an ordinary multimeter. The contact resistance is recorded on a test data sheet, and it is attached to the Saudi Aramco Pre-Commissioning Form, P-001, Switches; High and Medium Voltage Air, Oil, and SF-6. Increased contact resistance may be caused by contacts that do not make proper contact or by pitting on the surface of the contacts. The contact resistance values that are recorded should be consistent with the manufacturer's recommended values. Generally, values of contact resistance in excess of 150 micro-ohms and deviations of more than +/- 20% between adjacent poles or similar switches should be investigated. Technical data to evaluate the results of the contact resistance test can be found in the switch manufacturer's technical manual.


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Insulation Resistance The purpose of the insulation resistance test is to directly measure the insulation resistance of the medium or high voltage switch through use of a megger. In the insulation resistance test, the megger is used to set up an electromagnetic field, and the field that is created is used to produce leakage currents that will flow through the insulation between each phase and ground or from phase to phase. The amount of leakage current flow that is detected by the megger results in a megger meter readout of insulation resistance (in megohms). To conduct the insulation resistance test, the megger is connected between two of the blades of an open switch, and the megger is operated. Megohmmeter test voltages vary for medium and high voltage systems. Manufacturer's technical manuals should be consulted for the proper megohmmeter test value. In general, the values of insulation resistance should be less than the manufacturer's minimum values or less than the rated voltage of the system + 1 kV in megohms. Insulation resistance evaluation information is provided in Work Aid 2. Similar megger readings are taken between each remaining phase pair combination on both sides of the open contacts of the switch. The megger is then connected between each switch blade and ground, and the megger is operated. Similar megger readings are taken between each remaining phase and ground combination on both sides of the open contacts of the switch. The insulation resistance values are recorded on a test data sheet or in the Saudi Aramco Pre-Commissioning Form, P-001, Switches; High and Medium Voltage Air, Oil, and SF-6. Acceptable insulation resistance values should be determined through use of the manufacturer's technical manual. The insulation resistance test should only be performed the commissioning of switches and during the first few maintenance cycles. After maintenance cycles, the hi pot test is used to determine the integrity of the insulation switch.

switch during a few of the

Oil Dielectric Oil is used in some medium and high voltage switch installations as the arc quenching medium. The oil that is used as an arc quenching medium must have the ability to insulate the contacts, to quench the arc, and to dissipate the heat that is formed when the arc is developed. Because of the importance of the oil in the operation of switches that use oil, certain tests should be performed on the oil upon initial installation and during periodic maintenance periods.


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The purpose of the electrical tests and inspections that are performed on insulating oil is to ensure that the insulating oil has the correct dielectric properties to perform the arc interruption and that no impurities are present in the oil. A large array of testing is performed on oil prior to shipment and upon receipt; however, these tests generally fall into two categories: electrical tests of the oil's dielectric properties and tests for the presence of impurities. The electrical tests of the oil's dielectric properties test the dielectric breakdown voltage and the power factor of the switch oil. Tests for the presence of impurities, such as moisture and gas, are performed because the presence of impurities in the oil has a negative impact on the dielectric properties of the oil. The approved methods that are used to perform each of the tests are provided by the American Society of Testing and Materials (ASTM). ANSI C57.106 - 1991 contains the ASTM test reference information and the technical data that are necessary to evaluate the results of the oil dielectric inspection and tests. High Potential Both ac and dc high potential (hi pot) tests can be performed on medium and high voltage switches and switchgear. The purpose of the ac hi pot test is to evaluate the condition of the medium or high voltage switch insulation. Insulation that is in good condition will have sufficient dielectric strength to withstand voltage surges that are caused by switching or transient line surges. The ac hi pot test is used during the maintenance cycles of the switch to verify the proper condition of the switch insulation. The ac hi pot test is a go/no-go test, and it will not identify insulation that is gradually deteriorating. In general, the ac hi pot test can be performed on the same test points as the insulation resistance test; however, the frequency with which the ac hi pot test is performed differs from the insulation resistance test. The ac hi pot test is performed through the use of an ac hi pot test set. The leads of the test set are applied to the same test points as the leads in the insulation resistance test. The manufacturer's technical manual must be consulted to determine the appropriate test voltage for the test. Once the appropriate test voltage has been determined, it should be applied to the switch to test the insulation for a period of one minute. The ac hi pot test set measures the amount of current that leaks through the insulation of the medium or high voltage switch. When the leakage current reaches a predetermined amount, an overcurrent relay inside the test set is actuated, and a light is lit on the test set that indicates insulation failure. Sparks or arcs around the test leads also indicate insulation failure. If any of these test conditions occur, the switch needs to be replaced.


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The purpose of the dc overpotential (hi-pot) test is to identify internal faults in or damage to the electrical insulation. The dc hi-pot test should be performed prior to the initial energization of a medium or high voltage switch and after the megohmmeter test. The dc hi-pot testing technique involves increased dc voltage that is applied to the system under test. The value of the leakage current is measured and tracked as the test voltage is increased through several steps. This value becomes a criterion of the condition of the insulation. Electrical test reference information for the ac and dc hi-pot tests is provided in the Saudi Aramco Pre-Commissioning Form, P-000, Testing Guide Lines. The electrical test reference information provides the recommended test procedure and test voltages for the various equipment voltage ratings. During the test, the leakage current is plotted against time at the end of each timing interval. The ac or dc hi-pot test information is recorded on a test data sheet or in the Saudi Aramco Pre-Commissioning Form, P-001, Switches; High and Medium Voltage Air, Oil, and SF-6. Ac and dc hi-pot test evaluation information is provided in Work Aid 2. The Electrical Engineer should evaluate the ac and dc hi-pot test leakage current test data to ensure that the test data meet the minimum requirements for a successful test. A polarization index value of two or greater or ac or dc hi-pot test data curves that indicate a steady increase in leakage current over the duration of the test should be investigated by the Electrical Engineer who performs the test data evaluation.


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SYSTEM PRE-OPERATIONAL CHECK-OUT The system pre-operational check-out phase of the commissioning cycle for medium and high voltage switches provides an opportunity for Saudi Aramco personnel to perform wiring checks, subsystem component check-outs, and switch interlock performance tests. Each medium and high voltage switch component is checked to ensure that it works individually and as a complete system. Point-to-Point Wiring Check Point-to-point wiring checks are performed to verify medium and high voltage switch compliance with wiring diagrams and manufacturer specifications. Terminations and terminal blocks are also checked for routing and labeling. During the point-to-point wiring checks, terminations, supports, and fuses are checked for proper application and type. Subsystem Check-Out Subsystems are checked to ensure that electrical continuity exists for operational and control devices. The proper operation of all subsystems is tested by means of the controlled operation and check-out of the devices. An example subsystem operation and check-out is to operate the motor of a three-phase, motor-operated, disconnect switch. Each subsystem is performance tested through the application of full operational voltage to each subsystem through the proper protective devices (if applicable). A complete operational test is performed on equipment controls, interlocks, protective devices, and components with each subcircuit connected to its main system. During the performance test, the main systems are still isolated and independent from plant systems. Before the equipment is connected to the plant system, subsystem performance testing is critical to ensure the proper and safe operation of the equipment protection and control subsystems. Because phasing of power supplies is critical to the proper operation of rotating equipment loads (e.g., pumps and motors), the proper phase sequence at each of the power supply terminals must be checked and verified against the phase sequence of the connected loads. Interlocks Operation tests are performed to ensure that the medium and high voltage switch operational interlocks function properly. For example, if the switch has a key interlock, the proper operation of the key interlock should be tested. When a key interlock is tested, it should be tested to ensure that operation of the switch is possible with the key and that operation of the switch is not possible without the key. Any other operational interlock devices on the switch that can prevent the operation of the switch should be tested in a similar manner.


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SYSTEM OPERATIONAL TESTING The operational testing phase of the commissioning cycle for medium and high voltage switches provides an opportunity for Saudi Aramco personnel to perform the following: • Source Feed Compatibility Checks • Complete System Functional Test Source Feed Compatibility Source feed compatibility checks are performed on medium and high voltage switches through application of the full system voltage onto the installed medium or high voltage switch. With the voltage applied, voltage phasing, synchronizing, device rotation, and other source feed compatibility checks are performed. Both the preferred and the emergency power sources are connected to the loads to ensure the total operation of the major component loads of the system. Complete System Functional Test The operational testing of a medium or high voltage switch ensures that all of the installed parts, such as linkages and jaws, are able to work in conjunction with each other so that the switch and the installed equipment can provide electrical system protection and operation. Most of the tests that have been performed thus far have been tests that ensure the performance of the individual parts of the switch. The complete system functional test will ensure that the parts will work together so that the switch will operate correctly when it is installed in an electrical system. A complete system functional test is performed on medium and high voltage switches to ensure that the entire electric power system functions in accordance with the system design. During the complete system functional test, the equipment is allowed to assume a fully loaded condition for a period of time that is adequate to obtain the maximum system temperature. After the loaded time period, the equipment temperatures are monitored. Equipment temperatures can be monitored locally through use of temperature monitoring equipment or through use of thermographic surveys. Temperature monitoring equipment can be temporarily installed at the enclosure or switchgear vents. Particular attention should be paid to wiring and terminal connections during the complete system functional test.


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Because there may be several ways to operate a switch (e.g., manually by hand or with an operating motor), each mode of operation must also be tested to ensure that it properly functions. The complete system functional test must also include the proper operation of all interlocks (e.g., key interlocks) that are associated with the switch. The complete system functional test information is recorded on a test data sheet or in the Saudi Aramco Pre-Commissioning Form, P-001, Switches; High and Medium Voltage Air, Oil, and SF-6. During the complete system functional test, the inspector should visually assess that all of the contacts of the switch have opened as far as possible without grinding, scraping, or motion restrictions.


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WORK AID 1:

REFERENCES FOR EVALUATING MEDIUM/HIGH VOLTAGE SWITCHES UPON RECEIPT

The information that is presented in the checklists and information tables has been assembled from SAES-P-116, 16-SAMSS-510, ANSI C37, GI-2.710, and related industry standards. Figure 10 shows a table of Saudi Aramco general requirements for manually operated, dead-front, pad-mounted switches that are equipped with either separable connectors or other terminating means for ac systems.

General Requirements

Either separable connectors or other buyer specified means may be used to terminate the cable at a load interrupting switch. All energized parts of a dead-front pad-mounted switchgear (PMSG) must be insulated and completely enclosed within a grounded shielded system when separable connectors are in place. The Vendor must provide equipment that is sufficiently derated to operate at nameplate rating under the following temperature conditions (in addition to the temperature rise that is caused by Vendor's supplied equipment when it is operating at the nameplate rating): • Monthly Normal Maximum Ambient Temperature: 45 deg C • Enclosure Internal Temperature Rise Due to: (a) Solar Effects: 8 deg C (b) Internal Heater (if applicable): 3 deg C Total 56 deg C Equipment that is supplied in accordance with 16-SAMSS-510 must be protected from corrosion and operational failure when operating under the following conditions: • Normal air-borne dust concentration must be considered as 1 mg/m3 with 95% of all dust particles being less than 20 micrometer diameter. • Compounds present in the dust include those of sodium, calcium, magnesium, silicon, and aluminum. • Other pollutants present (worst case): H(2)S 20 ppm, SO(2) 10 ppm, CO 75 ppm, (NO(x) 5 ppm, and hydrocarbons 100 ppm. Figure 10: Saudi Aramco Requirements forPad-Mounted Switchgear with Load-Interrupting Switches


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Figure 11 shows Saudi Aramco load interrupting switch voltage ratings.

Rated Maximum Voltage (kV) 3 ø Switches

1 ø Switches

Rated Withstand Impulse Voltage, kV

15.5

8.9

95

27

15.5

125

38

21.9

150

Figure 11: Voltages and Insulation Levels for Load Interrupting Switches (From ANSI C37.72 - 1987)

Figure 12 shows Saudi Aramco load interrupting switch load, cable charging, and magnetizing interrupting ratings. Rated Voltage - kV Maximum 3ø 1ø Switches Switches 15.5 15.5 27 27 38 38

8.9 8.9 15.5 15.5 21.9 21.9

Continuous and Load Interrupting Current Amperes, rms 600 200 600 200 600 200

Cable Charging Interrupting Current, Amperes, rms 10 10 15 15 20 20

Magnetizing Interrupting Current, Amperes, rms 21 7 21 7 21 7

Figure 12: Load, Cable Charging, and Interrupting Current Ratings (From ANSI C37.72 - 1987)


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Figure 13 shows a table of Saudi Aramco guidelines for the application and the selection of load interrupting switches.

General Requirements

Operational Requirements

Load interrupting switches must not be used except with the prior written approval of the Manager, Saudi Aramco Power Distribution Department. Pad-mounted switchgear (PMSG) with load interrupting switches must be designed, rated, manufactured, and tested in accordance with the latest issue or revision of ANSI/IEEE Standard C37.72 - 1987 or IEC 298. Rated insulation levels and current ratings that are applicable to air switches must be in accordance with ANSI C37.32 or IEC 298. All switches must be group-operated. Switch operating mechanisms must be protected from damage due to weather, dust, and corrosion. For outdoor units, the switch mechanisms, linkages, and springs should be located inside tanks or enclosures. Synchronism check devices must be provided in situations where it is possible to interconnect two systems out of synchronism. For industrial applications, a blown fuse should initiate the opening of an associated switch. Switches must be of dead-front construction. Load interrupting switches must be capable of breaking currents that are equal to the continuous current rating of the switch at the rated system voltage and load. Load interrupting switches must be capable of interrupting small inductive or capacitive currents for applications in which the switch is used to disconnect unloaded transformers, cables, or overhead lines. Load interrupting switches must be capable of performing a closing operation onto a terminal short circuit. Load interrupting switches must have independent operators.

Figure 13: Guidelines for the Application and Selection of Load Interrupting Switches


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Figure 14 shows the construction requirements for medium and high voltage switch types from 16-SAMSS-510, ANSI C37.72 - 1987, and ANSI C37.32.

Frame-Mounted Load Interrupting Switch (Oil-Filled)

Pad-Mounted Switches

The frame-mounted load interrupting switch (oil-filled) is only suitable for outdoor use. Cable terminations must be of dry-type, dead-front construction. Potheads must not be used. The cable type must be specified by the purchaser so the switch manufacturer can furnish the correct terminal parts. For high making and breaking capacity, the switch must incorporate either a spring toggle mechanism or some form of arc control. Regular maintenance of this type of switch is necessary to remove accumulated sludge and to test the quality of the oil. Askarel or any polychlorinated biphenyl (PCB) dielectric (insulating fluid) must not be used. Refer to 16-SAMSS-510 for pad-mounted load interrupting switch specification requirements. Pad-mounted switchgear that uses switches in gas-filled sealed tanks is preferred over air-insulated switchgear. Vacuum switches are the preferred type of switching device in pad-mounted switchgear. Cable terminations must be dead-front, 600 A, separable, insulated connectors (elbows). Two threaded 1/2 in., #13 National Course (NC) bosses must be provided at opposite sides of the enclosure. Switch operating handles must be able to be padlocked in any position. Switchways must be provided with three positions. For switches that have on, off, and ground positions, the ground position must have the same withstand rating as the main switch. The switch mechanism must be such that switching from on directly to ground is not possible. Switching must be from on to off and then from off to ground. A separate interlocked ground switch may be provided to meet this switch mechanism requirement. The moving parts of switch operating mechanisms (e.g., springs) must be located inside the switch enclosure and protected from exterior environmental conditions. Switches that include a ground position must provide position indication that is similarly distinctive to the open and closed positions.

Figure 14: Construction Requirements for Medium and High Voltage Switch Types


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Pad-Mounted Switches (Continued)

Metal-Enclosed Interrupter Switchgear

Bolts, hinges, and associated hardware must be of Type 300 Series stainless steel. Mounting frames and enclosing panels must be constructed of bolted galvanized steel. Gasketing materials and adhesive must be suitable for the environmental conditions specified in 3.2.1. All exterior surfaces must be painted and must meet the requirements of ANSI C57.12.28 - 1988, Pad-Mounted Equipment - Enclosure Integrity, Section 5 - Enclosure Coating System, except the paint color must preferably be white with light grey an acceptable alternative. Nameplate(s) must be on the side of the enclosure. The following information must be included and may be on a separate nameplate: 1) Buyer's purchase order number 2) Manufacturer's location 3) Manufacturer's order reference number Nameplates must be in the English language according to American usage. Danger and warning indicators must be written in both Arabic (Naskh script) and English, utilizing white characters on a red background. Outdoor use of air-insulated interrupter switchgear is not allowed in new Saudi Aramco installations.

Figure 14: Construction Requirements for Medium and High Voltage Switch Types (Cont’d)


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For consistency, rated insulation levels and fault-make ratings that are applicable to air switches (as defined in ANSI C37.32) must be used for loadbreak switches. Figure 15 shows the preferred ratings for medium- and high-voltage loadbreak switches that are used by Saudi Aramco.

Rated Withstand Voltage Rated Maximu m Voltage (kV rms)

4.76 8.25 15.0 15.5 25.8 38.0

Impulse 1.2x50ms Wave (kV Crest)

60 75 95 110 125 150

60 Hz kV rms

Current Rating (amperes, rms) Interrupting and Continuous 200 400 600 1200

Wet (10 Sec) 15 24 26 30 40 --

Fault Make and Momentary Asymmetrical Current Ratings, kA, rms1 20 20 40 61 20 20 40 61 20 20 40 61 20 20 40 61 -20 40 61 -20 40 61

Dry (1 Min) 19 26 36 50 60 80

1 Short-time current ratings include a momentary and a three-second current rating that is based on test conditions that are described in section 5 of ANSI/IEEE C37.34. Divide the momentary rating by 1.6 to obtain the three-second current rating. When a higher momentary current rating than is shown is required, use a switch that has the next higher continuous current rating. Figure 15: Load Interrupting Switch Preferred Ratings (From C37.32-1990)


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Medium and High Voltage Load Interrupting Switch applications Checklist Medium and high voltage switch rating information can be found on the equipment nameplate or in the switch manufacturer's technical manual. The following is a checklist that is used to verify that the type, the rating, and the operational characteristics of a switch are correct for the application based on Saudi Aramco and industry standards: • Verify that the switch meets the Saudi Aramco requirements that are shown in Figures 13 and 14. • Verify that the switch frequency rating is correct for the application. • Verify that the switch rated maximum voltage is correct for the application: - Rated continuous current at 60 Hz - Rated load interrupting current - Rated momentary, making, and one-second current - Rated cable charging interrupting current - Rated magnetizing interrupting current • Verify that the switch impulse withstand voltage (BIL) is correct for the application. • Verify that the switch operational characteristics will provide adequate protection for the electrical equipment that is in the circuit with the switch (e.g., fuse rating). Switch rating information can be found on the switch nameplate or in the manufacturer's technical manual.


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WORK AID 2:

REFERENCES FOR EVALUATING MOTOR VARIABLE SPEED DRIVE INSTALLATION AND TESTING

The information that is presented; has been assembled from SAES-P-116, 16-SAMSS-510, ANSI C37, GI-2.710, and related industry standards. Figure 16 shows a Saudi Aramco Pre-Commissioning Form, P-001, Switches; High and Medium Voltage Air, Oil, and SF-6. P-001 contains a checklist and data tables for visual, mechanical, and electrical inspections, as well as mechanical and electrical tests, of medium and high voltage switches.


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Figure 16: Saudi Aramco Pre-Commissioning form, P-001, Switches; High and Medium Voltage Air, Oil, and SF-6


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Figure 16: Saudi Aramco Pre-Commissioning form, P-001, Switches; High and Medium Voltage Air, Oil, and SF-6 (Cont'd)


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Information, Formulas, and Tables for Use in Evaluating the Results of Insulation Resistance (Megger) Tests The results of all commissioning megger tests that are performed must be documented on the appropriate Saudi Aramco pre-commissioning form. A short time (1 minute) megger test is performed. Figure 17 shows the recommended megger test voltages for various equipment voltage ratings. Equipment Voltage Rating

Recommended Megger Test Voltage

100 - 250

500

251 - 600

1000

601 - 2500

2500

5000 +

5000

Figure 17: Recommended Megger Test Voltages

Figure 18 provides bolt torque values for bus connections. Bolt Size #8 - 32 #10 - 32 1/4 x 20 5/16 x 18 3/8 x 16 1/2 x 13

Tightening Torque 10 - 15 inch pounds 15 - 20 inch pounds 5 - 7 foot pounds 10 - 12 foot pounds 18 - 20 foot pounds 40 - 50 foot pounds

Figure 18: Bolt Torque Values for Bus Connections


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AC or DC Hi Pot Tests The ac and dc hi pot tests are high potential voltage tests that are conducted phase to ground and phase to phase. The tests are conducted from both the line and the load side of the open breaker contacts. The ac and dc hi pot test voltages must be in accordance with the manufacturer's recommended values. When the manufacturer's recommended values are not available, the maximum voltage values in the table in Figure 19 should be used:

Equipment Rated kV

Test Voltage kV AC DC

2.5

5.0

9.0

5

9.35

16.0

15

26.0

44.0

25

43.0

73.0

35

60

102.0

Figure 19: Table of Hi Pot Test Values

For the dc hi pot test, apply an initial voltage step of about one-third of the recommended maximum voltage and maintain the initial voltage for ten minutes. After the initial ten-minute test, the dc test voltage is increased in ten uniform steps up to the maximum recommended dc value. Each step should be held for one minute. For the ac hi pot test, increase the test voltage at a rate of 1 kV per second until the maximum recommended test voltage is reached. Field test voltages are determined by the following: ac test volts = 0.75 x (2.0 x rated voltage + 1kV). Information, Formulas, and Tables for Use in Evaluating the Results of Hi-Pot Tests During the performance of hi-pot testing, the test should be stopped if one of the following situations occurs: • The duration of the test has expired. • A rapid rise in leakage current occurs.


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The following are the characteristics of a satisfactory hi-pot test: • The leakage current decreases over time. • The leakage current increases on a straight line as voltage is increased. No "knee" is noticeable in the leakage current curve. An example of hi-pot test data is shown in Figure 20. Figure 20 shows both good and bad insulation test data.

Figure 20: Example of Hi-Pot Testing (Good and Bad Insulation)


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The following is an excerpt for GI 2.710, New Construction Check List Example, that illustrates the overall checklist and sign-off for major pieces of electrical equipment. 3.

Electrical Equipment All substations, power cable, electrical equipment, including lighting and wiring, to be checked for proper application, operation, and grounds. Distribution panels, switches properly identified, and all energization certificate requests signed.

Construction Agency

Power Distribution Dept. Project Inspection Commissioning (Note 1)


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Figure 21 shows an excerpt from GI 2.710, General Instruction Manual, that illustrates the inspections and tests that should be performed in major pieces of electrical equipment prior to the turnover of a facility.

Figure 21: GI 2.710 Excerpt


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Figure 21: GI 2.710 Excerpt (Cont'd)


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GLOSSARY BIL

The basic impulse insulation level (BIL) is the reference impulse level, expressed in full wave kilovolts, that the equipment can withstand without a flashover.

dielectric absorption ratio

The ratio of two timed insulation resistance readings (such as a 60-second reading that is divided by a 30-second reading).

grounding switch

A ground switch is a mechanical switching device by means of which a circuit or piece of apparatus may be electrically connected to ground for maintenance and safety reasons.

group operation

A group operation is the operation of all poles of a multiple-pole switching device

(ganged operation)

by one operating mechanism. Group operation is in contrast to single pole operation in which the number of operations required to reposition the device is equal to the number of poles.

load current

The highest rms current (in amperes) between unity and 0.8 power factor (lagging)

interrupting rating

that a loadbreak switch must be required to interrupt at the rated voltage and frequency for the expected operating life of the switch.

maximum direct current

The rms total current, which includes the transient direct-current component.

nominal system voltage

The nominal system voltage refers to the general equipment voltage class designation.

polarization index

The ratio of a ten-minute insulation resistance reading divided by a oneminute insulation resistance reading.

rated continuous current at 60 Hz

The amount of current that can be continuously carried by the equipment without exceeding the equipment allowable temperature rise.

rated maximum voltage

The highest rms voltage for which the equipment is designed, and it is the upper limit for operation.


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rated voltage

The highest nominal system voltage on which the equipment is intended to be applied.

rated withstand voltage

The voltage that the equipment must be able to withstand without flashover or other electric failure.


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Commissioning Switches, Medium & High Voltage

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