OK. The 4-1, 4-2,4-3 & 4-4 are 125v relays and these are used in the Emergency Push button trip circuit. The contacts from these relays are then used in a 2 from 4 circuit which takes it's 24V power from the three TCEA cards in a high select circuit. The 24V power is then used to energize the ETR & PTR Relay drivers (See Page 59). (Be careful, there is a small mistake on this drawing. The JLX/Y/Z relays are from XYZ on the TCEA cards not RST as shown on the drawing.)

So the logic is that any Emergency Push Button operating will dump 4-1/2/3/4 and dump the 24V signal to the PTR & ETR relays thus tripping the master protective.

Hope this is clear, please reply

 

Hello Glenmorangie, thanks for replying.

As we can see in our drawing of the pushbutton circuit trip, 4-1/2/3/4 relays are on the TCTG card and when we look at the card we can't find them (physically). we only can see the oranges relays (K22/23/24/25, we can read on the relay 24 Vdc), which are related with 4-1/2/3/4 relays according to the drawings Emergency Trips circuit on the <P> core TCTG card (As shown on that drawing D-49 GEH-6195B, 4-1:K22 / 4-2:K23 /4-3:K24 / 4-4:K25). it means that these are the same relays, are we right on that? if these are the same how it is possible to feed 24Vdc relay with 125Vdc?

Thanks for your helps and your patience, looking forward for your reply.

 

Give me an Email address at [email protected] and I'll send you a copy of GEH 6195D which is a later version.

 

CTLP,

I don't have a TCTG card in front of me, but if I recall correctly the 4-1, 4-2, 4-3 and 4-4 relays are the small, orange relays on the TCTG card. The coils of the relays are 125 VDC coils, but the contacts of the relay are connected to the P24VR power supply (of the TCTG card) and the P24VR-4 circuit that supplies the PTRs and ETRs (Primary Trip Relays, and Emergency Trip Relays). Relays have coils which operate at a particular voltage or voltage range; and the relay contacts also have ratings--how much voltage and/or current they can handle when opening and closing and when closed.

The other relays (the large relays with clear plastic covers)on the TCTG card are for the PTRs and ETRs and the synchronizing circuit. They have 24 VDC coils (nominal 24 VDC...), but some have 125 VDC passing through the relay contacts.

The P24VR power supply is high-selected using diodes on the TCTG card from 24VDC power supplies on each of the three TCEA cards. Unfortunately, I don't believe GEH-6195B shows the diodes and the supplies from the three TCEA cards (I have Rev. B and Rev. H; Rev. B doesn't show the 24 VDC power from the TCEA cards; Rev. B does...). Also, these Signal Flow Diagrams were not always the best drawings; I think the K22/K23/K24/K25 relay designation for the P24VR-4 relays may be in error (again, I don't have a TCTG to look at and refer to, but we all know the GE documentation can be "hit and miss"-both).

The P24VR-4 "bus" is the power source used for other relays (PTRs, ETRs, synch relays) on the TCTG card. Without the E-Stop circuit being picked up, no power can get through the 4-1/4-2/4-3/4-4 2-out-of-4 circuitry so that a failure of one of the "4" relays on the positive side of the supply or the negative side of the 125 VDC trip pushbutton circuit will not trip the turbine (there's that redundancy thing again--this is what separates the Speedtronic turbine control panel from most other PLCs or turbine control systems: redundancy in critical circuits).

Hope this helps!

I have a suspicion there is more to this question, though ....

 

Hi CSA,

I had a private conversation with these guys and learned something myself. The 4-1/2/3/4 relays are 24v coils. If you look at the drawing each pair of relays are connected in series with 2 large 8K resistors also in series all across the 125v supply (just above the orange relays). That's what was confusing the guys, 24v relays on a 125v supply! GE sometimes have some strange ways of doing things!

 

glenmorangie,

THANKS VERY MUCH for clearing this up! It's one for the memory bank.

There's usually a reason for everything--the hard part is finding who knows the reason. There are so few of the people who designed the Mark V left working in Salem, and things like this don't get passed on.

So, again, thanks very much. I've never taken the time to actually look at the ratings of the little orange relays. (I never had the time, actually! Or a reason....)

 

Thanks CSA for replying too. indeed we had that doubt about 24vdc relays in a 125vdc circuit. we finally arrived to a sensible answer to it, thanks to you both.

Greetings, and again was really helpful to read about the logic of the trip master relays 4.

 

CTLP,

Thank you for the feedback!