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Earth switch
- Thread starter Indy
- Start date
RRaghunath
Electrical
I have seen the fixed type 33kV switchgear that comes with a three position switch: Service-Disconnected-Earthed. Wonder why it should be different with 11kV fixed switchgear.
Dear Mr. Indy (Industrial)(OP)6 Nov 21 08:22
"...1) Is it a requirement to have an earth switch fitted on 11kv fixed pattern switchgear as a contractor is saying 2) an earth switch is only applicable to withdrawable switchgear."
1. The IEC standard does NOT stipulate that it is a requirement to have an earthing switch fitted on 11kV fixed pattern switchgear or a withdrawable switchgear. Very often (but not a must) that it is usual with cable incoming or outgoing to have an earthing switch. It is to discharge the cable (for safety reasons) before allowing for man to work on the cable. Note: other effective earthing means are also allowed.
2. Earthing switch can be applicable on a fixed or a withdrawable switchgear.
3. Note: a) for fixed gears, the breaker MUST be open before the earthing switch can be closed; (mechanical + electrical interlock).
b) for withdrawable gears, the breaker must be withdrawn before the earthing switch can be closed; (mechanical + electrical interlock).
4. Attention! The earthing switch MUST NOT be able to close when the breaker is in closed position.
Che Kuan Yau (Singapore)
"...1) Is it a requirement to have an earth switch fitted on 11kv fixed pattern switchgear as a contractor is saying 2) an earth switch is only applicable to withdrawable switchgear."
1. The IEC standard does NOT stipulate that it is a requirement to have an earthing switch fitted on 11kV fixed pattern switchgear or a withdrawable switchgear. Very often (but not a must) that it is usual with cable incoming or outgoing to have an earthing switch. It is to discharge the cable (for safety reasons) before allowing for man to work on the cable. Note: other effective earthing means are also allowed.
2. Earthing switch can be applicable on a fixed or a withdrawable switchgear.
3. Note: a) for fixed gears, the breaker MUST be open before the earthing switch can be closed; (mechanical + electrical interlock).
b) for withdrawable gears, the breaker must be withdrawn before the earthing switch can be closed; (mechanical + electrical interlock).
4. Attention! The earthing switch MUST NOT be able to close when the breaker is in closed position.
Che Kuan Yau (Singapore)
- Thread starter
- #4
Dear Mr. Indy (Industrial)(OP)
BTW following are for information only.
It is fine but costly to have earthing switch on every breaker panel. An acceptable practice in Europe is to install " earthing boss " of tinned copper on all phases of outgoing/incoming cable connections. Earthing is by means of a "portable earthing kit " comprising of a voltage indicator rod, operating rod and an earthing conductor (rated for the kA 1s) with three arms for connection on to the earthing boss each and a joint point with one conductor with a G-clamp for connection to the earth bar.
A MV board would consist of number of panels but needs only one set of portable earthing kit. Earthing bosses and one set of portable earthing kit cost is minimal in comparison to install earthing switch on every breaker panel.
Che Kuan Yau (Singapore)
BTW following are for information only.
It is fine but costly to have earthing switch on every breaker panel. An acceptable practice in Europe is to install " earthing boss " of tinned copper on all phases of outgoing/incoming cable connections. Earthing is by means of a "portable earthing kit " comprising of a voltage indicator rod, operating rod and an earthing conductor (rated for the kA 1s) with three arms for connection on to the earthing boss each and a joint point with one conductor with a G-clamp for connection to the earth bar.
A MV board would consist of number of panels but needs only one set of portable earthing kit. Earthing bosses and one set of portable earthing kit cost is minimal in comparison to install earthing switch on every breaker panel.
Che Kuan Yau (Singapore)
MV indoor switchgear in ANSI world there is a device called a ground and test breaker. It is designed to rack into the front switchgear, in place of a breaker. There are 6 stabs, which are isolated from line/load and phase to phase. It is set up so voltage can be checked live or dead. Also useful for phasing. This same device can also be used to safely ground the line or bus.
Not cheap. I checked for a client recently and for 15kV gear it was in excess of $40k.
Not cheap. I checked for a client recently and for 15kV gear it was in excess of $40k.
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