Electrical Panel Test
Electrical panels, which are widely used in all types of substations and industrial applications, include all secondary devices such as measuring elements, control switches, signaling, & secondary protections (overcurrent, earth fault relays, etc.).
The electrical panel test in any power system is performed to ensure that the panel construction, connection, and performance are correct from an operational, reliability, and safety standpoint; thus, to make sure the continuity of electrical operation, a complete panel test is performed in the factory, during commissioning, and during maintenance programs, applying a range of panel test procedures.
Visual Inspection
- Verify Fabrication Enclosure dimensions (as per approved drawing): height, width, and depth.
- Verify the Panel Main Name Plate.
- Verify the panel rating plate using the serial number provided.
- Check paint shade matches authorized drawing.
- Verify component make and type against BOM requirements.
- Verify bus bar material, size, color code, support, and clearance for
- Phase to Phase (Φ-Φ) &
- Phase to Neutral (Φ-N) as per drawing.
- Verify the mechanical lock rack’s in/out functioning using the handle for easy movement of the breaker.
- Verify VCB test position, service position control circuit, and legends.
- Check breaker rating sticker and serial number against approved drawing.
- Inspect the spring charge motor and shunt coil rating stickers.
- Check VCB shutter operation.
- Check spring charge with the appropriate handle.
- Verify wire and cable specifications, including make, size, color code, ferrule, and loose connections.
- Check component specifications based on drawings.
Control Circuit Tests
- Check the continuity of all control wires and check it was done according to the drawings.
- The control circuit receives control voltage via the power pack 110VDC.
- Turn ON the control supply by utilizing the battery-based power pack.
- The breaker operation is verified using the indication bulb.
- Red indication lamp: Used to check whether the circuit breaker is turned on.
- Green indication lamp: Used to check that the circuit breaker is turned off.
- Blue indication lamp: Used to check the breaker’s spring charge condition.
- Amber indication lamp: Used to check the trip state of the breaker.
- White indication lamp: Used to check the trip circuit’s health.
- Push to close manual: Check the breaker’s closure manual functionality.
- Push to trip manual: Check the breaker’s open manual functionality.
Auto Trip
The breaker will automatically trip when a fault occurs. For testing purposes, short the terminals in terminal block. The trip indication lamp will illuminate.
Healthy Trip Indication
Cubicle Lamp
The cubicle lamp is attached to the panel’s door limit switch and turns on/off automatically when the door is opened/closed.
This can be changed depending on the consumer’s requirements.
Anti-Pumping
When closing the circuit breaker, verify the anti-pump relay by holding the TNC (Trip Neutral Close Switch) in the closed position.
This indicates that the breaker must not be closed if the TNC is in the closed position. This ensures that the anti-pumping relay was functioning properly.
Truck Interlock
When the breaker is ON, the truck cannot move. When the truck is in the test/service position, the breaker cannot be turned on.
Space Heaters
To examine space heaters, change the thermostat’s temperature range to match room temperature.
Minimum Voltage Tests
Tripping & closing coil operation must be tested with different percentages of control voltage.
- 77V is 70% of 110V DC (Tripping alone operation).
- 93.5V is 85% of 110V DC (Tripping & Closing operation).
- 110V is 100% of 110V DC (Tripping & Closing operation).
- 121V is 110% of 110V DC (Tripping & Closing operation).
Current Injection Tests
RY-Over Current Fault
Short the R and Y bus bars in the outgoing terminals. The appropriate current injection kit injects current into the R/Y terminal.
The ammeter checks the injected current.
In the event that the current is injected above the prescribed value, the breaker will trip at a certain time.
If the current exceeds the high set point, the breaker will trip immediately.
YB – Over Current Fault
The YB – over current fault technique is the same as for the RY – over current fault.
Earth Fault
Inject phase current between any of the phases.
When the current is injected exceeding the programmed value, the breaker trips at a specific moment.
If the Earth fault is set to high, the breaker will trip instantly.
The ammeter must be checked by comparing it to the injected switch at every phase using the Ammeter switch.
When the panel is subjected to a current injection test, the Energy Meter can be examined by viewing the blinking pulse.
Contact Resistance Tests
This is used to measure the resistance of panel’s breaker contacts.
A current of 100A DC is applied to the R-phase breaker contact, with the resistance specified in contact resistance kit.
This method is repeated for the remaining Y and B phases.
The resistance will be measured in microohms(µΩ).
According to Ohm’s law,
V = I R
V = 7 x 10-3
V = 100 * R
7 x 10-3 = 100 * R
R = 70 μohms (µΩ).
Table for contact resistance test (limit <30µΩ).
| Phase | mV – Voltage Drop in millivolt | µΩ – Resistance |
| R | ||
| Y | ||
| B |
Insulation Resistance Test (IR Test)
Breaker Condition: ON
- To determine the insulation resistance between R, Y, and B to Earth.
- To determine the insulation resistance from R to Y, Y to B, and B to R.
Breaker Condition: OFF
- To determine the insulation resistance between R to R, Y to Y, and B to B phases.
- The above tests will be performed before and after the high voltage test.
High Voltage Tests
Breaker condition: ON
Precaution
- Verify that the breaker was in the service position.
- Check that the breaker is turned ON.
- Verify that the panel & high voltage kit are correctly earthed.
Procedure
Step-1: Short the Y and B stages and link to the earth.
Step-2: Before supplying power, ensure that the earth is properly connected by shorting the earth rod & the kit’s phase. If the earth was properly connected, the kit would trip.
Step-3: The relevant kit then supplies 50kV to the R-phase for 1 minute.
Step-4: Check to see if there is any flash (or) puncture.
Step-5: The leakage current will be indicated on the high voltage kit. (Limit <4 mA)
Step-6: If the leakage current exceeds the limit, examine the clearance between phases and the earth.
Step-7: The similar technique is followed for the subsequent phases.
Breaker condition: OFF
Precaution
- Confirm that the breaker was in the service position.
- Verify the breaker in the OFF position.
- Confirm that the panel is correctly earthed.
Procedure
Step-1: The 2 ends of the bars are short. And one end is attached to the earth.
Step-2: For one minute, the opposite end of bus bar is supplied with 50kV.
Step-3: The leakage current shall be noted. If the leakage current exceeds the limit, the clearance needs to be checked.
Step-4: The high voltage test is performed in the OFF status to ensure that the breaker is exactly open and that the interrupter can resist the high voltage.
PT Ratio Tests
- To apply 415V to the primary of the PT.
- To measure the voltage on the secondary side of the PT using the ratio 11kV/RT3/110V/RT3.
Applicable Standards
- IEEE 43: Standard for testing insulation of electrical equipment.
- NFPA 70B: Describes methods and equipment used for insulation testing.
- IEC 60364-6: Details how continuity tests should be performed.
- NFPA 70E: Covers operational checks of equipment for safety and functionality.
- IEC 60060: Guidelines for high-voltage testing techniques.
