WAZIPOINT Engineering Science & Technology: How Carry Out the Quality Inspection Test for Electrical Installation?

Wednesday, January 8, 2020

How Carry Out the Quality Inspection Test for Electrical Installation?

Quality Inspection Test

Quality Inspection Test is Obligation to Handover the Electrical Installation Project to the Client

Visual Inspection Test, Insulation Resistance Test, Hi-pot or High Voltage Injection Test, Primary Current Injection Test, Secondary Current Injection Test and Metering Current Transformer Polarity Test is the significant testing and commissioning requirements for any electrical installation. Also, Safety and Risk Control is the first priority task to supervisor or project manager to carry the project minimizing the hazards.

Visual Inspection Test:

Visual inspection test generally jointly with customer will be carried out at equipment installation site on the LV switchboard, where physically check to :)

  • Checking the layout of fitted components as per requirement following the local or international standards; 
  • Checking the overall dimension and sub-dimension  for each installed equipment like- switchboard, size of busbars, cable & cable trench, earthing conductors and location of feeder entry and takeoff point;
  • Checking and verify with client's requirement the product brand and origin, model, and circuit identification of installed components like- breakers, CT-PT (Current Transformers-Potential Transformer), fuses, ammeters, voltmeters, power meters and protection relays etc;
  • Checking overall paint, coating and galvanizing work, door and cabinet locking device, door gasket, door hinges, door cut-out holes as per required IP ingress protection rating;
  • Checking the busbar, cable & conductor termination point, all nut-bolt tightening; the marking & identification ferules , busbar safety clearance and phase gap between exposed live conductor, base angle bar and plinth;
  • Checking the labels & markings, name plate and phase identification as safely and correctly.

Insulation resistance Test

Carry out insulation resistance test using 500V meggar for LV (Low Voltage) equipment phase to earth, neutral to earth, phase to neutral and phase to phase to measure the insulation resistance with all breakers or switches in ‘ON’ positions.

All reading must be recorded in approved record sheet and finally produce a  Quality Assurance Test Report.


Megger Range Selection Criteria of IR Test:

Insulation testers with test voltage of 500, 1000, 2500 and 5000 V are available. The recommended ratings of the insulation testers are given below:

Voltage Level
IR Tester
500V DC
2.5KV DC
66Kv and Above

High Voltage Injection or Hi-Tot Test

Hi-Pot or high voltage test normally uses to check in any leakage or  weak point near to leakage, generally applied test voltage is three times of rated voltage. Low voltage switching equipment high voltage test carried out using 500V meggar test between each stressed phase and all other phase connected to exposed conductive parts with all breakers in ‘ON’ positions.

Applying 2.5kV AC voltage between each stressed phase and all other phase connected to exposed conductive parts of low voltage equipment for 60 seconds and measure the leakage current.

Primary Current Injection Test

The primary current injection test procedure generally followed as- 
01. Temporarily short for testing purpose all phases the R, Y, B and neutral N primary bars on one side of the protection CT (current transformers).

02. Connect the primary injection test set on R-phase and neutral N on primary bars on the other side of the current transformers.

03. Secondary current is monitored connecting an ammeter to the R-phase of CT.

04. Spill current is monitored connecting a milli-ammeter to the earth-fault relay current coil. 

05. Spill current is recorded separately as injecting 50% and 100% of the CT ratio through the primary bars. Also at the same time, record the secondary current of the R-phase respectively.

06. All test from 1 to 5 should be repeated for all other B & Y phases and test data should be recorded in quality assurance data sheet.

Secondary Current Injection Test

The secondary current injection test procedure generally followed as- 
01. Selecting the current plug setting of IDMTL relay to the rated current of 5A and TMS of 0.1 for 3/10 characteristic.

02. Then inject secondary current of 5A to R-phase and adjust pickup current to 5A.

03. Then one by one inject 10A, 15A and 25A to R-phase and record on record sheet the tripping time respectively. Noted that the standard timing should be within+30% and -10%.

04. accordingly select the proposed current setting and adjust the pickup current.

All test from 1 to 4 should be repeated for all other B & Y phases and test data should be recorded in quality assurance data sheet. 

 Safety & Risk Control During Test

Safety Arrangement must comply all safety and risk control procedure, using the following four step risk management process may allow to consider risks associated with managing electrical risks in the testing workplace:

  1. Identify the hazard problem.
  2. Risk assessment or determine the level of risk to testing places and others as a result of the problem.
  3. find the risk control procedure or decide what needs to be done about the problem.
  4. Make sure that all are working as planned.

All test should be carried out following the procedure as below-

01. Safety barriers will be installed surrounding the area where the testing work is going to be carried out.
02. Tag in/ Tag out and sufficient danger signs will be hanged to warn the people who approach the testing area.
03. Visible warning lamp or flashing light should be confirm during supplying power to the board for testing
(D) First aid box and basic fire fighting  equipment will be placed for emergency usage at testing area.

1 comment:

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