Grouding System Field Test Procedure

ELECTRICAL TESTING PROCEDURES oo P roject T itle Project Title Principal Client Main Contractor SubContractor Doc Code:

Rev. No. OA

Date Issued: April 4, ‘07

Re Ref f. Ref.

: : : : :

GROUNDING SYSTEM FIELD TEST PROCEDURE

PREPARED BY PreComm DEPARTMENT

REVIEW ED BY QA/QC MANAGER

Pre-Comm SUPERVISOR

QA/QC MANAGER

REVIEW ED BY PROJECT MANAGER

REVIEW ED & APPROVED APPROVED BY

REVIEW ED & APPROVED BY BY

PROJECT MANAGER

1

M.H.R

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ELECTRICAL TESTING PROCEDURES

TABLE OF CONTENTS

Section / Description

Page No.

1.0

PURPOSE

3

1.0

SCOPE

3

2.0

DEFINITIONS

3

3.0 3.0

REFER EFERE ENCE NCE STANDA ANDAR RDS AND AND CODE CODES S

3

4.0

RESPONSIBILITIES

3

5.0

TEST EQUIPMENT CONTROL

4

6.0

CHECKS & TEST

4

7.0

TESTING PROCEDURE

4

8.0

DOCUMENTATION

8





ELECTRICAL TESTING PROCEDURES DISCIPLINE :

ELECTRICAL

TITLE

PROCEDURE FOR SITE ACCEPTANCE TESTING OF GROUDING SYSTEM

1.0

:

PURPOSE

To ensure that the grounding system’s characteristics are within applicable standards and design specifications.

2.0 SCOPE This procedure shall apply during the site acceptance testing of grounding systems.

3.0

DEFINITIONS 3.1 3.2 3.3. 3.4.

4.0 4.0

Commissioning Engineer / Supervisor Construction Manager Testing Technician echnic ian Quality Control

REFE REFERE RENC NCE E ST STANDA ANDARD RDS S AND AND COD CODES ES 4.1. 4.1.

5.0

C.E. C.M. T.T. .T. Q.C.-

Qual Qualit ity y Cont Contro roll Spec Specif ifica icati tion on-El -Elec ectri trical cal Works orks

RESPONSIBILITIES 5.1 5.1 The The Comm Commiss issio ioni ning ng Engi Engine neer er / Supe Superv rviso isorr (C.E (C.E.) .) shal shalll be resp respon onsi sibl blee for for preparing the testing plan, for the observance of all safety precautions required by the CCC Safety Plan, for supervising the testing activities. He shall prepare the testing testing plan that will include the equipment to be tested, tested, the tests to be performed, performed, the test equipment equipment to be used, the test procedure to be applied and the test records to be used. Based on the testing plan, in coordi coordinat nation ion with with the Constru Constructio ction n Manage Managerr a testing testing schedu schedule le will will be developed. The The Commis Commissio sionin ning g Engine Engineer er / Superv Superviso isorr shall shall organ organize, ize, superv supervise ise and verify the implementation of the testing schedule. Any defects or variances from the approved specification and standards will





ELECTRICAL TESTING PROCEDURES





ELECTRICAL TESTING PROCEDURES 5.3

6.0

The QC QC Department sh shall be be respo sponsible for for conducting ing reviews of of the test records to ensure that all tests have been performed in accordance with the approved inspection and test plan.

Test Equipment Control The Commissio Commissionin ning g Engin Engineer eer / Superv Superviso isorr shall shall carry carry out an inspec inspectio tion n of the test equipment when the test equipment arrives in the warehouse. Each piece of the test equipment shall have the calibration labels intact. He shall ensure that test equipment manual is available and that the test equipment is calibrated and calibration certificates are available. He will maintain maintain a record with the test equipment equipment serial numbers, date of calibration and copies of calibration certificates. The Commissioning Engineer shall ensure that test equipment that it is out of calibration is isolated in a quarantine zone and will be sent as soon as possible to a certified metrology laboratory for re-calibration against national standards. The Testin Testing g Technici echnicians ans shall shall ensure ensure that that the test test equipm equipment ent is tested tested for proper proper operation before starting any test. Any defective test equipment will be isolated in a quarantine zone and sent as possible for repairs. QC Depart Departmen mentt shall shall conduc conductt period periodic ic checks checks on the test equipm equipment ent to ensure ensure all equipment is within the required calibration period. The following test equipment will be used to perform the above tests: 1. Cali Calibr brat ated ed tor torqu quee wren wrench ch 2. Earth Earth resistan resistance ce test set AVO or Metrawa Metrawatt tt 3. Digi Digita tall mult multim imet eter er

7.0

CHECKS & TEST The Testing Testing Technician shall use the applicable Saudi Aramco Test Report SATR SATR & precommissioning form P-012 as a checklist and record the results of the testing. The form shall be the quality record document to identify that the inspection and testing has taken place. The following tests will be performed and recorded on the Saudi Aramco precommissioning form P-012 1. Visual isual and and mechan mechanical ical insp inspecti ection on 2. Two poin pointt met metho hod d 3. Fall Fall of pote potent ntia iall meth method od

8.0

TESTING TEST ING PROCEDURE PROCEDURE





ELECTRICAL TESTING PROCEDURES 8.1

Visual and Mechanical Check   

8.2

Check the conformance of the grounding system to drawings and specifications. Check that the grounding electrodes locations and the grounding conductor’s sizes are as per drawings and specifications. Torque check all the connections and joints of the grounding cables to grounding bars and grounding electrodes.Torquing electrodes.Torquing values shall be as pre ARAMCO pre-commissioning form P-000 Two-point method

Test Equipment: Earth resistance test set AVO AVO or Metrawatt  

 



  

8.3

This method is employed for measuring the resistance of a single grounding electrode or in congested areas where finding room to drive auxiliary electrodes may be a problem. The method uses an auxiliary grounding electrode whose resistance is either known or can be measured. Grounding Alternating current or DC may be used conductor Auxiliary for this test. rod The resistance for the auxiliary grounding electrode must be very small Grounding compared to the resistance of the driven electrode grounding electrode so that the measured value can be assumed to be wholly Earth contributed by the driven ground resistance electrode. test set The lead resistances will be measured Fig.1 and should be deducted from the final measurements. The connections for the test are shown in fig.1 The reading obtained is that of two grounds in series. This method is usually a “go or no go” test. Fall of potential method

Test Equipment: Earth resistance test set AVO AVO or Metrawatt   

This method measures grounding electrode resistance based upon the principle of potential drop across the resistance. It uses two auxiliary electrodes: one is the current rod and one is the potential rods that are placed at a sufficient distance from the test electrodes. A current of known magnitude is passed through the electrode under test and the current rod. The drop in potential between the electrode under test and the potential rod is measured.







ELECTRICAL TESTING PROCEDURES 

 

The goal in precisely measuring the resistance to ground is to replace the auxiliary current electrode far enough from the grounding electrode under test so that the potential rod will be outside of the effective resistance areas of both the grounding electrode and the current rod. The test connection is shown in fig.2. The best way to found out if the potential rod is outside the effective resistance areas is to move it between X and Z and to take a reading at each location Current supply

Voltmeter

Ground Electrode Under test

auxiliary potential X electrode

R RR

Ammeter

Y

auxiliary current electrode

Z

EARTH

Fig.2 



If the potential rod is located outside of the effective resistance areas the reading variation is minimal. If the potential rod is in an effective resistance area or if the effective resistance areas overlap the readings will vary noticeable in value as shown in fig.3. The reading should be plotted to ensure that they lie in a “plateau “region as shown in fig.4The r4egion is often referred to as the 62% area.

Fig. 1

X

Y’ Y”

Fig. 2

Z

X

Y’ Y”

Z





ELECTRICAL TESTING PROCEDURES applies for a homogeneous soil and an electrode of 1 inch in diameter. For an electrode of ½ inch the distance shall be reduced by 10% and for a 2inch diameter the distance shall increased by 10%.

Depth driven (feet)

Distance to Y(feet)

Distance to Z(feet)

6 8 10 12 18 20 30

45 50 55 60 71 74 86

72 80 88 96 115 120 140

Table 1 

In multiple electrode systems the distance between the auxiliary electrodes is based on the maximum grid distance. Table 2 gives the recommended distance values between the electrode under test and the auxiliary electrodes based on the maximum grid diatance. Table 2

Maximum grid distance (feet)

Distance to Y(feet)

Distance to Z(feet)

6 8 10 12 14 16 18 20 30 40 50 60

78 87 100 105 118 124 130 136 161 186 211 230

125 140 160 170 190 200 210 220 260 300 340 370





ELECTRICAL TESTING PROCEDURES acceptable to the tester used. The following methods could be employed to minimize the effect of stray voltage:  Braid the auxiliary cables together in order to cancel the common mode voltages between the two conductors.  Change the alignment of the auxiliary cables so they are not parallel to power lines.  Use shielded cables.

Voltmeter

earth resistance test set

Earth resistance Test set

ground rod Y

Z

Water screens

Fig.5



Fig.6

Excessive resistance of the current or potential electrodes can inhibit the test because the constant test current couldn’t be generated by the test instrument. To To ensure a good contact with the earth stamp down the soil directly around the auxiliary electrode to remove air gaps and pour water around the auxiliary electrodes.

Grouding System Field Test Procedure

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