In case of 6.6 kv HT board tripping ckt,when i press trip button it doesn't trip the vacuum contactor ckt..but trip ckt healthy goes off? what may be reason trip coil is found healthy??

check your current setting

That indicates the Battery is weak or the DC source has some loose connection.

Also check if the mechanical linkage of trip system is OK.Is it a vacuum contactor or breaker

Pl check trip push resistance of the tripping push?also check the v drop from trp push to coil?

thanx for all. @ prem hooda ji... how to check trip push resistance its is enclosed thru cable in adapter.

I think i you read the schematic, you have a trip coil monitor circuit in the form of a lamp. The power path is a connection from the positive bus (DC supply assumed) through a resistorized light, through an "A" (52a) contact through the trip coil. The 52a contact is common to both the trip trips and the light circuit, they are in parallel.

If the breaker (contactor) does not trip when you press the trip push button is because:

1. The fuse(s) are blown as in there is no power,

2. The 52A contact is not making (not closed) when the breaker is in the close position

3. The trip coil is open circuited.

How to check:

a. Is there status light to tell you you have power ?
b. Do an operational test. Manual trip the unit and electrically close it via the control switch and try tripping again. If it does not work trouble shoot the circuit.
c. Use a DVM on DC scale, put black lead on ground (assuming DC supply in center point ground through DC supply ground relay).
- remove trip coil monitor light from its socket.
- measure for -ve value at bottom terminal of trip coil, then top terminal of trip coil (or bottom of 52a) then top of 52a, bottom of trip switch contact. All reading should read negative value.
d. measure top of trip switch should read positive.

Please scan schematic, we can't read your mind on how it is wired and post it.

You may have a gammy trip coil/mechanical mech, and/or the loss of TCS may indicate a poor connection on the trip cct. BUT check the TCS schematic, pushing the trip button CAN create a TCS alarm on some basic TCS monitoring cct designs.

In that case can u fwd me dwg/photo of trip push & coil ? Resistance must not be more than .5 ohm of contact when making? Excluding the cable resistance?