690Vac Earth Leakage Tests

[PieterDen]

I have 690Vac MCC and must do earth leakage tests in the DRC, the standard test equipment can only do 550Vac phase to phase.
Is there any body with the same voltage? and that possibly assist.

 

[che12345]

Dear Mr. PieterDen (Electrical)
"...I have 690Vac MCC and must do earth leakage tests in the DRC, the standard test equipment can only do 550Vac phase to phase.
Is there any body with the same voltage? and that possibly assist."

1. It is unusual? to carry out "earth leakage test*" on a LV 690Vac MCC. Can this* test be replaced by "insulation resistance" test at 500Vdc or 1kVdc, plus "dielectric voltage" test at 2kVac ?
2. a) 500Vdc and 1kVdc "insulation resistance" test sets are readily/economically available on the market,
b) 0-5kVac "dielectric voltage" test set with/without leakage current meter in uA and with/without timer are readily/economically available on the market.
3. Refer to IEC test procedure, voltage level, duration , minimum insulation resistance in MOhm, and judgement on pass/fail on dielectric test, etc...
Che Kuan Yau (Singapore)

 

[PieterDen]

Thanks for your reply,This is a DRC mine but we operate as per the South African MHSA and we must test LV(690v) earth leakages on a monthly basis.

 

[che12345]

Dear Mr. PieterDen (Electrical)
"...Thanks for your reply, This is a DRC mine but we operate as per the South African MHSA and we must test LV(690v) earth leakages on a monthly basis...".
Che. Sir, my sincere apology for my ignorance. I have NO experience at all on electrical installations in mine, and what is a DRC mine. Not to mention South African MHSA regulation/requirement.
I am thinking that as it is a (test) that [MUST be done on monthly basis]; there must be numerous engineers that have this knowledge/experience and there must be plenty of suitable testing equipment that is in use/available in that location.
I am sorry for the inconvenience caused.
Che Kuan Yau (Singapore)

 

[Gr8blu]

Che: DRC Mine refers to a mine owned/operated by the Democratic Republic of Congo. South African MHSA is the Mine Health and Safety Act.

Pieter:
Earth leakage (aka ground leakage) is electric current that “leaks” to earth or ground via an unintended conductive path – usually through the insulation. When this occurs, a live phase comes in contact with the ground, creating a fault current that’s enough to activate the corresponding circuit breaker. In some cases, it may not result in a fault current right if the live phase comes in contact with a device that is not in contact with the earth. But the moment someone touches the device containing the live phase, the resulting fault current begins to flow through the person to the earth, resulting in what we call as electrocution.

Earth leakage can occur unintentionally or by design. More specifically, unintentional earth leakage may happen due to insulation or equipment faults. On the other hand, some electrical systems such as high-frequency fluorescent lighting and IT equipment normally produce small amounts of leakage under normal operating conditions. Regardless of the source, earth leakage must be tested and protected to prevent causing electric shocks. One protection method is to use an isolated power system (IPS) integrated with an insulation monitoring device. A more common method is by integrating an automatic disconnection of the supply (ADS), which is usually based on residual current devices (RCDs) or residual current circuit breakers with overcurrent protection (RCBOs).

Both RCDs and RCBOs monitor and compare the current flowing in the line and neutral conductors. Any difference in the measurements that exceeds the sensitivity setting or mA rating of the RCD or RCBO will cause the device to trip. Earth leakage protection works as well as intended most of the time. However, there are times when the RCD or RCBO device trips for no apparent reason, i.e. “nuisance” tripping. This is where the need for an earth leakage current testing arises.

If a nuisance trip problem exists, use an earth leakage clamp meter to measure the imbalance between the line and neutral conductors which is the total earth leakage of the system. An earth leakage clamp meter allows testing the circuit in a safe, fast and easy way. It is a handheld device that clamps around a conductor and will instantly give a reading of the actual leakage current. It can detect small currents down to 0.01 milliamp, so use this to find the problem circuit. From there, either isolate the broken circuit or go on to find out if there’s a particular problem appliance. Once the problematic circuit is located, figure out whether the earth leakage is intentional or unintentional. If unintentional or caused by a fault, the fault must be repaired. Intentional earth leakage may require some form of circuit splitting or load spreading.

Any competent person may test low-voltage circuits where the alternating current is below 1000 V. Where the electricity supply exceeds that limit or hard wiring is required, only a licensed electrician may conduct the RCD testing.

Converting energy to motion for more than half a century

 

[PieterDen]

Thank you, if possible I need info on the meter as per your description(earth leakage clamp meter allows testing the circuit in a safe, fast and easy way. It is a handheld device that clamps around a conductor and will instantly give a reading of the actual leakage current).

 

[Gr8blu]

Pieter:
You might try the following link to identify the best 300-series meter for your particular needs.

https://megger.com/earth-leakage-clampmeter-dcm300e

Or simply use your favorite search engine with the "earth leakage clamp meter" search phrase.

Converting energy to motion for more than half a century

 

[waross]

There are tests and there are tests. You have stated that the South African MHSA requires tests, but have not indicated what tests are required. Knowing what type of test is to be conducted and the allowable limits is the first step in selecting test equipment.



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Ohm's law
Not just a good idea;
It's the LAW!