Surge Arrest Test Procedures

DOC No: VEL/P/QAI/001 Rev :0 Date : 12-05-2006

VIJAI ELETRICALS LTD PROJECTS DIVISION HYDERABAD

INSPECTION MANUAL

ITEM: SURGE ARRESTERS


TYPES OF SURGE ARRESTERS & REFERENCE STANDARDS

Type of Surge Arresters 1. Distribution Class – 5 KA Surge Arresters without pressure relief arrangement 2. Intermediate Class – 5KA & 10KA Surge Arresters with pressure relief arrangement in a distribution class housing

3. Station Class a. Discharge class – I - 10 KA Surge Arresters with pressure relief arrangement b. Discharge class –II - 10 KA Surge Arresters with pressure relief arrangement c. Discharge class –III - 10 KA Surge Arresters with pressure relief arrangement d. Discharge class –IV - 20 KA Surge Arresters with pressure relief arrangement e. Discharge class –V – 20 KA Surge Arresters with pressure relief arrangement Reference Standards: 1. 2. 3. 4. 5. 6. 7.

IS:3070(part-3)-1985, IEC 60099-4(Part-4)(second edition) IS: 5621-1980 IS: 2071 (Part- I ) 1993 IS: 2071 (Part- II ) 1974 IS: 2071 (Part- III ) 1976 IS : 6209 -1982 DOC No: VEL/P/QAI/001 Rev :0 Date : 12-05-2006

I)

List of Type tests required for Distribution class Surge Arresters (5KA) Ref Stds: IS:3070(part-3)-1985,IEC60099-4(Part-4)(second edition)

1. Insulation Withstand tests a) Lightning Impulse Voltage Withstand test b) Power Frequency Voltage Withstand test 2. Residual Voltage Test a) Steep current impulse residual voltage test b) Lightning impulse residual voltage test 3. Long duration current impulse withstand test 4. Operating duty test ( High current impulse operating duty test ) 5. Power frequency voltage versus time curve

6. Arrester Disconnector (When fitted) 7. Artificial Pollution test II)

List of Type tests required for Station class Surge Arresters (10KA & 20KA) 1. Insulation Withstand tests a) .Lightning Impulse Voltage Withstand test b) Power Frequency Voltage Withstand test 2. Residual Voltage Test a) Steep current impulse residual voltage test b) Lightning impulse residual voltage test c.) Switching Impulse residual voltage test

3.

Long duration current impulse withstand test

4. Operating duty test ( High current impulse operating duty test ) 5. Power frequency voltage versus time curve 6. Pressure relief test 7. Artificial Pollution test


III. Routine Tests

a) Measurement of Reference voltage test b) Residual voltage test c) Partial discharges test d) Sealed leakage test

IV. Standard Acceptance Test a) Power Frequency reference voltage test b) Partial discharge test c) Residual Voltage test d) Leakage Current test e) Seal leakage test (Special test)

f) Galvanizing tests g) Special Thermal Stability test

DOC No: VEL/P/QAI/001 Rev: 0 Date : 12-05-2006

Surge Arrester Acceptance Test Procedures

Ref Stards:IS:3070(part-3)1993 & IEC 60099-4 Sampling Plan: Cube root of the quantity offered

1. POWER FREQUENCY REFERENCE VOLTAGE TEST: This test is carried on 9KV rated Arresters at resistive current crest value of 1mA by using a 300KV Power Frequency testing transformer. The measurements are made by using storage Oscilloscope. SL.No. of Arrester

250 350 450

Crest Value of Resistive Current (Ref. Current) 1mA 1mA 1mA

Reference Voltage K.V.(RMS)

11.00KV 11.00KV 11.00KV

Result: The Reference Voltage of the Arresters is greater than the rated Voltage (i.e. 9KV RMS). Thus the Arresters have passed the test

2. LIGHTNING IMPULSE RESIDUAL VOLTAGE TEST ON 9KV ARRESTERS: With the 9KV rated Arresters in circuit the impulse voltage generator is adjusted to deliver a current of 10KA – 8 x 20 micro second front time. The residual discharge voltages of 9KV Arrester units are measured at this current level. The measurement are made by using Oscilloscope.

The RDV of 9KV Arrester at 5KA are tabulated below : Sl.No. of Residual Discharge Voltage in KV(Peak) Arrester 250 28.08 KV 350 27.04 KV 450 27.04 KV 500 27.04 KV 560 27.04 KV

RESULTS: The Maximum Residual Discharge Voltages are well below the guaranteed Value (i.e. 32KV (Peak) at 5KA), thus the arresters have passed the test.

DOC No: VEL/P/QAI/001 Rev : 0 Date : 12-05-2006

3. PARTIAL DISCHARGE TEST :

This test is conducted on samples of 9KV rated Arresters as per IEC Publication-270 (Method of measurement of P.D. of high voltage apparatus) for satisfactory absence from partial discharges. The Power Frequency Voltage is applied to the Arrester Units from 300KV transformer. The voltage is increased up to rated voltage of 9KV and then decreased to 1.05 times MCOV i.e.., 8.0KV (RMS). At this voltage Partial Discharge is measured by means of P.D meter conforming to IEC Publication – 270. The results are tabulated below: Sl.No. of Arrester 250 350 450

Voltage applied KV (RMS) 8.0KV 8.0KV 8.0KV

P.D. Level Pc 5 Pc 5 Pc 6 Pc

Result: The Internal Partial Discharge is well below 10 pC which is the maximum as per the specification and thus the Arresters have passed the test. NOTE: In the above test procedure 9KV rating is taken as a sample


4. LEAKAGE CURRENT OF THE SURGE ARRESTER :

The leakage current is measured by using storage Oscilloscope at MCOV of the surge arrester. Compliance: It should be less than 300 micro amps or as indicated in the approved GTP.

5. a. SEAL LEAKAGE TEST: ( This test is performed by any sensitive method adopted by the manufacturer) Vacuum over Water (Dip Test) Method for distribution & Intermediate class Arresters. The Surge Arresters are completely immersed in water bath and subjected to a partial pressure of -350mm of Hg for not less than 2 ½ minutes to check the air leakage from the arrester. Continuous bubbling from the arrester is an indication of seal leakage. Subsequently the arresters are cleaned and tested for IR value by 5KV megger and the criteria for passing is that the IR value should not be less than 1G Ohm.


b. SEAL LEAKAGE TEST: ( This test is performed by any sensitive method adopted by the manufacturer)

Water (Dip Test) Method for station class surge arresters. The Surge Arresters are completely immersed in water bath .After a period of 30 minutes the surge arresters are lifted out & dried. Subsequently the arresters are cleaned and tested for IR value by 5KV megger and the criteria for passing are that the IR value is as follows: Arrester rating

9KV 10KA 12KV 10KA to 18KV 10KA 30KV 10KA to 42KV 10KA 60 KV 10 KA & above

IR value in G ohms

1G ohm (min) 2G ohm (min) 5G ohm (min) 8G ohms (min)


6.GALVANIZING TESTS : a) Test for Uniformity of Coating

Samples are selected at random . A solution of 360 grams of CuSO 4 in on liter of distilled water is prepared. The specific gravity of the test solution is adjusted to 1.18. The sample is subjected to four dips in the prepared standard solution, each dip lasting for one minute. After each dip the samples are cleaned with water and then dried . Result : After the last dip no copper deposition could be detected on test sample. The sample has passed the uniformity of coating test satisfactorily as per IS : 3070 (Part-III) of 1993 & IS: 2633-1986 b) Test for Mass of Zinc Coating by Stripping Method:

The Stripping solution is prepared as follows: Dissolve 20 g of antimony trioxide (Sb 2 O3) or 32 g of antimony trichloride (SbCl 2) in 1000 ml of concentrated hydrochloric acid. Immediately before test, prepare the stripping solution by adding 5ml of the solution prepared under above to 100ml of concentrated hydrochloric acid. Mix well. Prepare the test samples (preferable 20mm x 20mm or 40mm x 40 mm), the samples should be dry & clean . Take the weighment in mg, record the weight (M 1) . Then immerse the test piece in the stripping solution . When the evolution of hydrogen ceases or a few bubbles are being evolved, the test pieces shall be taken out, washed in water, wiped off well with clean soft cotton clothe , fully dried and weighed (M 2) again. Calculate the mass of zinc coating/unit area as below. Calculation : M = M1 – M2 x 106 A Where M = Mass of zinc coating in g/m2 of surface M1 = Original mass in g of the test piece, M2 = Mass in g of the stripped test piece, and A = Coated area of the original test piece in mm DOC No: VEL/P/QAI/001 Rev :0 Date : 12-05-2006

7. SPECIAL THERMAL STABLITY TEST

This test is done on three samples of ZNo Blocks / sections selected randomly from the current routine production and having the same dimensions and characteristics as those of the arresters under test. Adjust the generator charging voltage as per Table 4 of IS: 3070(Part-3)1993/Table 5 of IEC60099-4 (part-4) second editions for line discharge test Pre heat the block to 70 oC +/- 3 oC and then apply High current impulse (75Amps for 1000 microseconds for distribution class /)* , as short as possible (not longer then 100 milli seconds) apply rated voltage of the block of 3KV for 10 sec and then immediately apply MCOV (2.55 KV Rms) and monitor the leakage current for 30 minutes. Compliance: The leakage current of the ZNo block should be thermally stable * In case of station class surge arresters (Class-2,3,4,5) two long duration current impulses as per Table 5 of IEC60099-4 (part-4) second edition for line discharge test with an interval of 60 seconds between shots is applied References : 1. As per Figure 3 of IS : 3070 (part 3) of 1993 2. As per Figure 4 of IEC 60099-4 part 4

Surge Arrest Test Procedures

Recommend Documents