GIS 12-051 - Transformers and Reactors IEC - 0900a86680021f8

Document No.

GIS 12-051

Applicability

Group

Date

05 September, 2003

Guidance on Industry Standard for Power Transformers and Reactors (IEC)

GIS 12-051

BP GROUP ENGINEERING TECHNICAL PRACTICES

05 September, 2003

GIS 12-051 Guidance on Industry Standard for Power Transformers and Reactors (IEC)

Foreword This is the first issue of Engineering Technical Practice (ETP) GIS 12-051. This Guidance on Industry Standard (GIS) is based on the following heritage documents from merged BP companies:

BP RPSE GS 112-5

Guidance for Specification GS 112-5 Transformers and Reactors

Copyright  2003, BP Group. All rights reserved. The information contained in this document is subject to the terms and conditions of the agreement or contract under which the document was supplied to the recipient’s organization. None of the information contained in this document shall be disclosed outside the recipient’s own organization without the prior written permission of Manager, Standards, BP Group, unless the terms of such agreement or contract expressly allow.

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Table of Contents .......................................................................................................................................... Page Foreword.......................................................................................................................................... 2 1.

Scope...................................................................................................................................... 4

2.

Normative references.............................................................................................................. 4

3.

Design, materials and fabrication............................................................................................4 3.1. General........................................................................................................................ 4 3.2. Design considerations..................................................................................................5

4.

Materials and fabrication......................................................................................................... 5 4.1. Mechanical handling.....................................................................................................5 4.2. Tank and radiators........................................................................................................5 4.3. Insulating liquid............................................................................................................ 6 4.4. Winding terminations and connections.........................................................................6 4.5. Bushings...................................................................................................................... 6 4.6. External finish............................................................................................................... 7 4.7. Fittings......................................................................................................................... 7 4.8. Forced cooling equipment..........................................................................................11 4.9. Noise.......................................................................................................................... 11 4.10. Rating plates..............................................................................................................12 4.11. Tests........................................................................................................................... 12

5.

Drawings and documentation................................................................................................13 5.1. Information to be supplied with quotations.................................................................13 5.2. Information to be submitted after receipt of order.......................................................14

6.

Shipping................................................................................................................................ 14

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1.


Scope This GIS document provides guidance on industry standard for design, materials, fabrication, inspection, testing, documentation, and preparation for shipment of IEC power transformers and reactors.

2.

Normative references The following normative documents contain requirements that, through reference in this text, constitute requirements of this technical practice. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this technical practice are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies.

IEC International Electrotechnical Commission IEC 60034 IEC 60076-1 IEC 60076-3 IEC 60076-5 IEC 60076-8 IEC 60076-10 IEC 60137 IEC 60214 IEC 60289 IEC 60296 IEC 60354 IEC 60529 IEC 60542 IEC 60616

3. 3.1.

Rotating electrical machines Power transformers – Part 1: General Power transformers – Part 3: Insulation levels, dielectric tests and external clearances in air. Power transformers – Part 5: Ability to withstand short circuit Power transformers – Part 8: Application guide Power transformers – Part 10: Determination of sound levels Insulated bushings for alternating voltages above 1000 V On-load tap-changers Reactors Specification for unused mineral insulating oils for transformers and switchgear Loading guide for oil-immersed power transformers. Degrees of protection provided by enclosures Application guide for on-load tap-changers Terminal and tapping markings for power transformers

Design, materials and fabrication General a.

Performance guarantees shall be provided on: 1.

No load losses.

2.

Full load losses.

3.

Percent impedance, both positive and zero-sequence between various windings.

4.

Percentage regulation at 100% and 80% power factor.

b.

Oil-immersed distribution transformers shall be fabricated in accordance with relevant parts of IEC 60076.

c.

Reactors shall be fabricated in accordance with relevant parts of IEC 60289.

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d. 3.2.


Polychlorinated Biphenyl (PCB) contamination of insulating liquid shall not exceed one part per million (PPM). PCB PPM shall be recorded on permanent nameplate.

Design considerations a.

Temperature rise shall comply with IEC 60076-2.

b.

Insulation levels shall comply with IEC 60076-3 table 2. The short duration power frequency withstand voltage is a single figure related to the maximum expected system voltage of the winding (Um). Because industrial systems are generally connected via underground cables, the lightning withstand voltage can be selected as the lower of the two options given in IEC 60076-3. However where fed via overhead lines, the higher of the two values should be chosen.

c.

Short circuit withstand shall comply with IEC 60076-5.

d.

Liquid immersed transformers shall be rated with cyclic duty capacity as specified in IEC 60354.

e.

Transformer and reactor control cabinets shall be IP55, in accordance with IEC 60529.

f.

If data sheets specify a load rejection overvoltage, the transformer shall be designed to safely withstand the resulting conditions without damage or causing mal-operation. Manufacturer shall specify a transformer secondary voltage that is expected following a load rejection condition. Note that some expected overvoltages for load rejection on unit connected generator transformers can be severe. Protection arrangements also need to be taken into consideration (fifth harmonic restraint). The voltage appearing at the secondary terminals of the transformer can also impinge onto standard distribution transformer primary windings and these should be assessed. Hence the manufacturer is required to assess the transformer secondary voltage under conditions of load rejection.

4. 4.1.

4.2.

Materials and fabrication Mechanical handling a.

Transformers and reactors shall be designed to facilitate skid movement in any direction without use of rollers, planes or rails.

b.

Lifting and jacking points shall be mounted on tanks and arranged to prevent damaging stresses during lifting and jacking operations.

c.

Tank covers shall not distort when lifted.

d.

An informational plate shall be mounted on the tank, when spreader bars are required for lifting all or part of the tank.

Tank and radiators a.

Liquid immersed transformers and reactors shall be fitted with filling and draining orifices.

b.

Tank drain-off orifice of conservator transformers shall be fitted with a valve.

c.

Devices fixed to the tank or tank lid above insulating liquid level shall have a stand-off lip to prevent water tracking to the interior of tank.

d.

Covers of sealed tank transformers shall be welded to tank.

e.

Gasketed joints, with the exception of pressure relief devices, shall be below cold liquid levels. Page 5 of 14

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4.3.


f.

Filling and draining orifices shall be sealed with screwed plugs.

g.

Expansion space above liquid level in a sealed tank transformer shall be filled with an inert gas.

h.

Construction and sealing arrangements of sealed tank transformers shall be such that internal pressure shall not exceed 0.5 bar (g) negative and 0.7 bar (g) positive for a top liquid temperature range from –25ºC to +100ºC.

i.

Maximum and minimum operation pressures shall be indicated on the rating plate.

j.

Removable radiators shall be provided with isolating valves and screw plugs for venting and draining.

k.

Tanks shall be fitted with at least one earthing boss complete with 12 mm diameter brass bolt and phosphor bronze washers.

Insulating liquid a.

Unless otherwise requested on the data sheet, insulating oil shall be mineral type complying with the test requirements of IEC 60296. Note that the data sheet gives the alternative of having liquids of various fire rating. Such liquids can be specified for some offshore applications.

4.4.

4.5.

b.

Silicone is an acceptable alternative.

c.

Nameplate shall identify insulating liquid.

d.

Transformers and reactors shall be shipped filled with insulating oil when ever possible.

e.

Transformers and reactors shipped unfilled shall be designed for vacuum filling in field.

Winding terminations and connections a.

Taps and winding connections shall be based on principles specified in IEC 60076-1, IEC 60076-4 and IEC 60214.

b.

Internal connections and those passing through tank wall shall be located below cold liquid level.

c.

Terminals for receiving external connections shall be marked in accordance with IEC 60616.

d.

Connections having pinch screws bearing directly on conductor are not acceptable.

Bushings a.

Bushing shall comply with IEC 60137. Where tropical conditions are to be catered for it is important to specify this on the data sheet.

b.

Unless otherwise indicated on the data sheets, creepage distances shall be suitable for heavy polluted atmospheres, as defined in IEC 60137. Very heavy pollution is sometimes addressed by coating insulators with a grease. This type of treatment is considered unusual for general Industrial applications and should only be considered for voltages above 132kV in heavily polluted areas. The selection of heavy pollution is considered suitably conservative for most applications however this may be reduced to Medium if the site is considered not to be subject to a heavy pollution.

c.

Bushings connected to overhead lines shall be equipped with arching horns or surge diverters.

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4.6.


d.

Current rating of bushings and connections from transformer windings shall be rated at least 20% higher than current tap settings of transformers.

e.

Routine 60 second AC withstand-test voltage for bushing shall be at least 10% higher than transformer applied/induced test.

External finish Finish of transformer and reactor enclosures shall be ANSI 61, or equivalent, consisting of: a.

Corrosion-resistant metal primer.

b.

Durable machinery/enamel finish.

4.7.

Fittings

4.7.1.

Control and alarm contacts

4.7.2.

4.7.3.

4.7.4.

a.

Settings on instruments and protective relays shall be directly visible. Contacts shall be suitable for making or breaking not less than 150 VA between the limits of 30 V and 250 VAC or DC.

b.

Contact insulation and that of associated terminals shall be capable of withstanding an applied voltage test of 2 kV r.m.s. for 1 minute, both between individual circuits, and between individual circuits and instrument or relay case.

Disconnecting chamber

a.

Transformers shall include a means for testing cables connected either to HV or LV windings. Disconnecting chamber provided for this purpose shall be separate from transformer tank and for sealed tank designs, it shall not be possible for an interchange of liquid with main tank.

b.

Liquid filled disconnecting chambers shall be provided with separate drainage facilities and an external indication of liquid level. Terminals and their gaskets shall be located below the cold liquid level.

External terminations

a.

Cable boxes shall be arranged so that they can be removed from transformer without breaking the cable seal or affecting sealing of tank.

b.

Where an air filled cable box is fitted, the terminal arrangement shall be phase insulated, phase separated, or phase segregated. Means shall be provided in all three types of cable box to facilitate fault pressure relief in such a manner as to direct fault arc emissions between the cable box and the main tank, to minimise danger to personnel.

c.

Cable boxes shall be provided with a gland plate with cable glands suitable for cables specified.

d.

Air-filled cable boxes shall be provided with a means of maintaining internal air at an adequate level of dryness.

e.

When a bus duct termination is required, it should be air filled and shall be phase insulated, phase separated, or phase.

Current transformers

a.

Current transformers shall be within either an appropriate disconnecting chamber or within a separate chamber similar to the disconnecting chamber and containing the same insulating medium.

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The details of any CT required to be supplied should be separately provided. This should co-ordinate with the protection arrangements. Where a CT is to be housed but free issued, these details similarly need to be separately provided. b. 4.7.5.

4.7.6.

4.7.7.

4.7.8.

Means should be provided to permit primary injection testing of current transformers.

Off-circuit tap-changers

a.

Off-load tap-changing equipment shall provide the high voltage winding with one principal and four constant kVA taps to compensate for supply voltage variations of ±2% and ±5%.

b.

Off-circuit tap-change settings shall be selected by an externally operated switch, with a clearly marked position indicator and mechanical stops to prevent over-running. Tap switch shall be pad lockable. Numbering of tap positions shall be such that an increase in number corresponds to a decrease in the effective number of turns on tapped winding.

On-load tap-changers

a.

On-load tap-changers shall comply with IEC 60214 and IEC 60542.

b.

On load tap changers shall be designed to ensure that when a step movement has commenced, it shall be completed independently of operation of control switches or relays. Limit switches and mechanical stops shall be provided to prevent overrunning the mechanism.

c.

A mechanically operated device shall indicate number of tap position in use. Numbering of tap positions shall be such that an increase in number corresponds to a decrease in the effective number of turns on tapped windings. A device shall be fitted to the tap change mechanism to indicate the number of operations completed.

d.

If automatic or remote voltage control of tap changer is required, the associated equipment shall be the subject of a separate specification.

Conservators

a.

Conservators shall be removable for transport purposes and equipped with a liquid level indicator, liquid filling hole with screwed plug, combined filter and drain valve, detachable end plate, lockable isolating valve and dehydrating breather.

b.

Conservator, complete with sump and drain valve, shall be in such a position as not to obstruct the electrical connections.

c.

Conservators shall have a capacity of not less than 8% of total cold liquid volume in main tank and cooling equipment.

d.

A sump shall be provided to prevent sludge and moisture from being drawn into transformer.

e.

Conservators shall be fitted with a prismatic or magnetic liquid level indicator, readable from ground level.

Valves

a.

Valves shall be provided with a position indicator, which shows clearly whether the valve is in the open or closed position.

b.

Means shall be provided to padlock each valve in the 'open' or 'closed' position.

c.

Drain valves and those provided for the connection of mobile liquid filtration equipment shall be provided with screwed plugs.

d.

At least one valve suitable for oil sampling (e.g. for DGA measurements) shall be fitted at an accessible location on the transformer tank.

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4.7.9.

4.7.10.

4.7.11.

4.7.12.

4.7.13.

4.7.14.


Dehydrating breather

a.

Breathing type liquid level containers shall be fitted with a dehydrating breather accessible from ground level.

b.

Breather shall not require recharging at less than six month intervals under the ambient conditions specified.

c.

A protective mesh screen with a minimum degree of ingress protection IP20 to IEC 60529, shall be provided around the breather.

Thermometer pockets

a.

Thermometer pockets shall be provided for all liquid filled transformers.

b.

Thermometer pockets shall have an internal diameter of not less than 15 mm, an internal depth of not less than 115 mm and be equipped with a sealing cap held captive by an external chain.

c.

The pocket should be welded into the transformer wall in a location where a thermometer will always indicate top liquid temperature.

Gas and liquid actuated relays

a.

Gas and liquid actuated relays shall be Buchholz type fitted for protection of conservator type liquid-immersed transformers.

b.

They shall be equipped with bolted flange connections to facilitate their removal for maintenance or repair.

c.

Design of relay and mounting arrangement shall be such that it will not sustain damage due to vibration under service conditions.

d.

Relay shall be equipped with facilities for permitting injection of liquid or air for testing purposes.

Pressure relief and indications devices

a.

Pressure relief devices shall be fitted to liquid-immersed transformers.

b.

Pressure relief devices fitted to sealed tank transformers and reactors shall be resetting rapid acting relief valve type fitted with a mechanical operation indicator. Device shall operate at a static pressure appropriate for the protection of tank, be mounted on tank cover and fitted with at least one pair of changeover contacts.

c.

Means shall be provided for directing emissions of liquid from the relief device in the direction specified.

d.

Sealed tank transformers shall be fitted with a pressure vacuum gauge indicating device equipped with one set of changeover alarm contacts.

Liquid level gauge

a.

Liquid-immersed transformers and reactors shall be fitted with a prismatic or magnetic type liquid level gauge.

b.

Liquid level corresponding to an ambient of 25C at no-load together with the maximum and minimum levels, should be permanently marked on the gauge.

Temperature indicators

a.

Temperature indicators shall be glass fronted and designed to not sustain damage or maloperate due to vibration under service conditions.

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4.7.15.

4.7.16.

4.7.17.


b.

The dials of temperature indicators shall have a preferred scale range from 30C to 150C (liquid-immersed transformers) uniformly divided. They shall an accuracy tolerance of ±1% between the highest and lowest scale reading.

c.

Temperature indicators shall have a maximum temperature pointer and an adjustable pair of changeover alarm contacts.

Liquid temperature indicators

a.

Liquid temperature indicators shall be fitted and arranged to indicate temperature of hottest liquid in transformer.

b.

Alarm contacts shall close at temperature value specified in table 2, and open when temperature has fallen by at least 7°C.

Winding temperature indicators

a.

Thermal image type winding temperature indicators shall be fitted for liquid-immersed transformers.

b.

Alarm and trip contacts shall close at temperature values specified in Table 1. Both sets of contacts shall open when temperature falls by at least 7C.

c.

If forced cooling or provision for forced cooling is specified, winding temperature indicator shall incorporate another set of electrically independent contacts for control of forced cooling equipment. Control contacts shall be adjustable to close between 50C and 100C and to reopen when temperature has fallen by 15C to 30C. Nominal settings for contacts are shown in Table 2.

Ancillary equipment terminations

a.

Ancillary equipment such as pressure relays or sensors, temperature relays or sensors, flow switches, and current transformers, which require external wiring, shall be wired to a marshalling box mounted on side of transformer and accessible from ground level.

b.

Marshalling box shall provide a degree of protection of at least IP55 to IEC 60529.

c.

Every contact of each relay, sensor or switch and every tap of each current transformer shall be wired out to marshalling box.

d.

Wiring to marshalling box shall be 2.5 mm2 (minimum) stranded copper conductors with insulation rated for 600/1000 V.

e.

Current transformer terminals shall be of the shorting type and sized to terminate 6 mm 2 copper conductors.

f.

Wiring to marshalling box shall be weatherproof.

g.

Cable entries shall be either from the bottom or sides.

h.

A blank gland plate shall be provided on bottom of marshalling box for external cabling.

i.

If forced cooling, or on-load tap-changing equipment is provided, an associated control cabinet may also be used for ancillary equipment terminations. TABLE 1 — ALARM AND TRIP TEMPERATURE SETTINGS ITEM

Windings

Type

Dry Type

INSULATION CLASS

ALARM C

TRIP C

A E B

100 115 120

115 130 135

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F H C

140 165 190

155 180 205

Windings

Liquid-Immersed

A

105

120

Liquid

Liquid-Immersed

A

100

-

TABLE 2 — FORCED COOLING NOMINAL TEMPERATURE SETTINGS TYPE

INSULATION CLASS

Dry Type

Liquid-Immersed

4.8.

Forced cooling equipment

4.8.1.

Forced air cooling

4.8.2.

SWITCH-OFF

C

C

A E B F H C

85 100 105 125 150 175

60 75 80 100 125 150

A

90

65

a.

Forced air-cooling shall be electric motor driven fans.

b.

Air ducting and fan protective covers shall be provided to prevent accidental contact with fan blades or other moving parts and to prevent ingress of harmful matter.

Forced liquid cooling

a.

Cooling system shall comprise either an integral or separate liquid cooling circuit.

b.

Both types of forced liquid cooling circuits shall be externally cooled by forced or naturally circulated air or water as specified.

c.

It shall be possible to isolate and remove separate coolers without reducing liquid level in main tank.

d.

Each cooler shall be provided with following:

e. 4.8.3.

SWITCH-ON

1.

Isolating valve at the liquid inlet and outlet.

2.

Liquid filling hole with screwed plug.

3.

Combined filter and drain valve.

4.

In-line flow switch in inlet of cooler complete with at least one set of changeover contacts.

It shall be possible to remove the pump and motor from both integral and separate liquid cooling circuits without drawing off liquid from main tank or cooling plant.

Fan motors

Motors shall comply with IEC 60034 for general purpose, continuously rated, weatherproof machines, selected for reliable service under ambient conditions.

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4.9.

4.10.


Noise a.

Noise level limits for naturally cooled liquid-immersed transformers shall be as shown on Figure 1.

b.

If a noise test is specified. testing shall be performed at manufacturer's works in accordance with IEC 60076-10.

Rating plates Rating plates for transformers and reactors shall comply with IEC 60076-1 and IEC 60289 respectively.

4.11.

Tests a.

Routine tests should be performed on all transformers and reactors.

b.

For liquid-immersed transformers and reactors, routine tests shall comply with IEC 60076-1.

c.

For earthing transformers, routine tests shall comply with IEC 60289.

d.

Rated Short Duration Power Frequency withstand voltage shall be selected from Appendix A of IEC 60076-3, for all types of equipment.

e.

Type tests and special tests shall be performed on selected transformers and reactors.

f.

Tests to be carried out shall be identified formally agreed with the purchaser.

g.

Sealed tank transformers and reactors shall be filled with liquid and subject to a hydrostatic pressure test of 1 bar (g) without loss of pressure, for 24 hours.

h.

Conservator type transformers shall be subjected to a hydrostatic pressure test of 0.3 bar (g) without loss of pressure, for 24 hours.

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FIGURE 1 — NOISE LEVELS, 'A' WEIGHTING

CURVE 'A' = 0.3 to 2.5 MVA, to 11KV ONAN cooled, cooling tubes or tank mounted radiators. CURVE 'B' = 2.5 to 15 MVA, TO 33KV, ONAN cooled, tank mounted radiators. CURVE 'C' = 7 TO 40 MVA, TO 33KV, ONAN cooled, separate radiators. (SOURCE: B.E.B.S. - T2 (1966)) 5.

Drawings and documentation Drawings provided for this equipment shall show equipment as specified and ordered. Typical drawings are not acceptable.

5.1.

Information to be supplied with quotations a.

Exceptions.

b.

Equipment or features not specified.

c.

Detailed descriptions of proposed equipment, accessories, and features.

d.

Equipment layout and dimensions.

e.

Lifting arrangements.

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5.2.

6.


f.

Jacking points.

g.

Total weight (including liquid if applicable).

h.

Cable entry positions.

i.

Volume of liquid.

j.

Location of ancillary equipment.

k.

Identification of “third party” components, equipment and systems.

l.

Price and availability of recommended spare parts.

m.

Itemized list of unassembled equipment including shipping splits and ship loose items.

n.

Cost for witness testing.

o.

Installation, maintenance and operating instructions.

p.

Type test certificates.

Information to be submitted after receipt of order a.

Size and location of conduit connections, cable entrances, and throats, referred to transformer centrelines.

b.

Location of grounding pad(s) and size of holes.

c.

Size and location of anchor bolts.

d.

Horizontal and vertical clearances necessary for dismantling and removing core and cover. Weights of the core and tank without oil should be listed.

Shipping a.

Manufacturer shall be responsible for the adequacy of the preparation for shipment.

b.

Components shipped separately shall be properly tagged to identify their final installation location.

c.

Components with moving parts which might be damaged in shipment, shall be securely blocked and braced to prevent damage.

d.

Shipping blocks, binding, etc., shall be clearly marked so that their removal is assured. Special precautions that must be observed in removal of shipping restraints shall be clearly marked on shipping container or crate.

e.

Complete installation instructions for any parts shipped separate from tank and core assembly shall accompany transformer shipment.

f.

Transformer shall be shipped filled with oil for normal 25C level.

g.

Shipments shall be identified with Company’s requisition and appropriation numbers and transformer tag number.

h.

Material Safety Data Sheet(s) (MSDS’s) for equipment shall be provided to shipper at time of shipping.

i.

MSDS’s shall conform to all relevant regulations where equipment will be located.

j.

If any chemical so shipped is exempt from such laws, a statement to that effect shall be included on MSDS.

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GIS 12-051 - Transformers and Reactors IEC - 0900a86680021f8

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