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Join Date: Nov 2009
Posts: 5

Connecting Three-Phase ELCBs

11/30/2009 4:47 AM

We know that on ELCB, incoming terminal is connected to the supply and the outgoing terminal is connected to the load. is it possible to connect it the other way? (load is connected to the ELCB incoming terminal and supply is connected to the ELCB outgoing terminal)

ELCB will trip when it detects unbalance current between phase and neutral. But does it detects on incoming side or outgoing side?

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#1

Re: Connecting 3-phase ELCB

11/30/2009 5:29 AM

yaa , it is possible but main function to installed ELCb for to survive load ckt against of earth fault protection & to get isolation of live ckt so if suppose do reverse connection load ckt can not protected against earth leakage

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Guru

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#2

Re: Connecting 3-phase ELCB

11/30/2009 6:11 AM

Earlier days, breakers had what is called 'Line-Load Bias" - (i.e.) Incoming had to be connected to the terminals marked Line and outgoing to be connected to the terminals marked Load.

But, thanks to advanced manufacturing technologies, todays' breakers do not have this line-load bias. That is - Incoming or Outgoing can be connected to any terminals, Top or Bottom.

However, ELCB function is not direction specific - It is rather the vector sum of the phase and the neutral currents. But, be sure to connect all incoming (phases & Neutral) to one side and all outgoing (Phase & neutral) to the other side.

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#3
In reply to #2

Re: Connecting 3-phase ELCB

11/30/2009 6:59 AM

yes it is not dirction specification but vector sum of phase & neutral current only

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Guru
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#4

Re: Connecting Three-Phase ELCBs

11/30/2009 11:57 PM

As electricalexpert65 says, the older devices had restrictions regarding Line/Load connections, which is no longer necessary. However, it is prudent to connect the incoming and outgoing if the manufacturer has distinctly merked the terminals as Line and Load. This may mean that the device is single-break per pole, and it is not desirable to keep the wrong side of it live when it is open. Why do you wnat to connect it the other way?

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#8
In reply to #4

Re: Connecting Three-Phase ELCBs

12/03/2009 9:04 AM

thank you for all the comments. i found this installation in my office. what makes me puzzled is the ELCB never tripped (as i've worked for almost 5 years), but i found a burning spot behind one of the MCB inside the same DB (distribution board). just thought maybe burning spot might caused by reverse installation of ELCB. just for your info, this DB is connected to heavy 3 phase machines and the machines operated 24 hours.

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Guru
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#9
In reply to #8

Re: Connecting Three-Phase ELCBs

12/03/2009 9:17 AM

The ELCB will not trip unless there is a leakage to earth. It will not trip on overloads and short circuits, the MCB is expected to trip in such cases, as you must be aware. The majority of faults (in India at least) are due to poor terminations, which can result in overheating, and sometime even escalate to visible arcs of low magnitude. Even these will not trigger the ELCB unless the arc strikes an earthed part. If you can study the installation in your office, you may be in a better position to find out what caused that burning spot.

There is one other possibilty for the ELCB not tripping .. it may have become defective mechanically..most manufacturers recommend that you test its health periodically by pushing the Test button. You may try that

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#10
In reply to #8

Re: Connecting Three-Phase ELCBs

12/03/2009 9:52 AM

If the ELCB has not tripped in five years, I would first compliment you that you are maintaining a perfect earth leakage free installation (unless the ELCB itself is faulty as has been told by KVS). The most probable cause of the burning spot behind the MCB is loose connection. Please check your termination for proper tightness. It doesn't matter if the MCB is connected to hecavy machinery and the machinery operates for 24 hours.

An addition though, if your three phase machinery is driven by three phase motors, then I have my own reservations as to the provision of an MCB as a switching cum back-up overload & short circuit protective device. I would rather prefer a Switch Fuse Unit, a contactor, an overload relay or an MCCB with a contactor & overload relay.

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#11
In reply to #10

Re: Connecting Three-Phase ELCBs

12/03/2009 1:56 PM

I agree with that burning spot is caused by poor termination. but i'm not sure whether the ELCB is faulty or the system is very good. it's because in my opinion, possibility of good system might make sense because:

1. The DB has the supply directly from UPS main switch board and is isolated from other loads (only for that machine area) and cabling structure is under raised floor and i think the possibility of poor insulation (bitten by rats or etc) of the laid cable is quite low.

2. If the was any earth leakage, and the ELCB was faulty, is it possible if the ELR or EF (outgoing to that DB) would trip?

3. Never had the chance to test the ELCB (by pushing trip button) because of the needs of continuous power supply by the clients (high cost involved if that area face any power interruption.

Just need other opinions for my own knowledge as I'm not very good in electrical.

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#12
In reply to #11

Re: Connecting Three-Phase ELCBs

12/03/2009 8:53 PM

Yes! I too opine that you must be maintaining a good system as I assume form whatever you have stated that the DB is feeding to three-phase loads where the chances of an earth leakage are comparatively lesser.

1. Is the Secondary Neutral of the UPS bonded to Earth seperately? If it is not, then even if there is a severe earth fault, the ELCB or ELR will not trip, as the system downstream of the UPS becomes an ungrounded system. Please ensure this.

2. If this ELCB can turn faulty, there are equal chances of any other ELCB or ELR (outgoing to that DB) might also be faulty. So, do not depend on the outgoing side ELCBs.

3. The regular testing of ELCBs by pressing the Push Button is not by CHANCE but you MUST do it on a regular basis. No excuses on that front. Because earth leakage is something to do with the safety of human lives, no sort of production pressure, however large it might be, would justify the non-testing of the ELCB. Because, the entire protection to the life of humans having access to this system depends on the proper functioning of this ELCB. So, please do test the ELCB very regularly.

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#5

Re: Connecting Three-Phase ELCBs

12/01/2009 6:38 AM

Why?

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#6

Re: Connecting Three-Phase ELCBs

12/01/2009 9:53 AM

Every manufacturer has a reason why they mark input supply and output supply on their products.even if u can interchange and get same result,just FOLLOW THE SPECIFIED CONNECTION METHOD and get yr job done.Remember that someone else may not understand it in yr own way and may get into trouble to handle such or similar device if u are not around.

Just connect the device in the specified manner.It helps others to continue from where u stop.U may hv same result here,but u may not hv same result in some other devices,so take precautions in all installations.

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#7

Re: Connecting Three-Phase ELCBs

12/02/2009 4:15 PM

If this is an AC breaker, it is a non-directional device. However, the protective system may be directional sensitive. For example, the breaker may have a reverse power relay, or the overcurrent protection may be voltage restrained or have a directional element (this type will only trip on overcurrent in a specific direction). It may also be part of a differential protection scheme.

In any of the above cases, the polarity of the current transformers must be carefully reviewed to ensure the breaker will trip properly on a fault. Also, adjacent differential schemes are designed to overlap their protection zones to ensure all faults are detected. The transformer secondary breaker in a substation will be part of both the transformer protection and the distribution bus protection. The CT's in the secondary breaker for each area will be on the far side of the breaker from the protected zone, so that a fault in the breaker itself will be detected and isolated.

Lastly, a DC air-insulated breaker using magnetic blowout coils IS polarity sensitive. If it connected in reverse, the breaker opening arc will be blown down into the contacts instead of up into the arc chute.

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#13

Re: Connecting Three-Phase ELCBs

12/04/2009 12:44 PM

Are MCBs directional?

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Guru

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#14
In reply to #13

Re: Connecting Three-Phase ELCBs

12/04/2009 7:52 PM

No! MCBs too are not direction specific today. There is no line-load bias in today's MCBs.

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#15
In reply to #14

Re: Connecting Three-Phase ELCBs

12/09/2009 12:37 PM

what is arc-chute?does ELCB has one and if it had where is it located (inside the ELCB)?

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Guru
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#16
In reply to #15

Re: Connecting Three-Phase ELCBs

12/09/2009 7:35 PM

Please see this thread wherein some discussions are there ....

Arc divider

kvsridhar

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cik beskot (3); electricalexpert65 (4); giri (1); kvsridhar (3); Patrick Whowha (1); pwr2thepeople (1); PWSlack (1); tmp_patel (2)

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