Synchronization Questions 3

[nightfox1925]

We are going to commission a 600V double ended switchgear with N.O. tie and all synch and control logic will be initiated by a Universal Relay: GE C60. I have some confusion when it comes to the Synch-check function settings of this relay which are:

-Synchronization max voltage difference
-Synchronization max angle difference
-Synchronization max frequency difference
-Synchronization max freq hysteresis
-synchronization dead source select
-synch dead V1 source max voltage
-synch dead V2 source max voltage
-synch Live V1 min voltage
-synch Live V2 min voltage

I read the GE manual for these descriptions and still doubtful. Does anyone had any typical settings for these functions or at least educate me a bit on them?

How does the terms LiveV1/LiveV2, DeadV1/LiveV2, DeadV1/DeadV2, DeadV1Xor(exclusive OR)DeadV2 and deadV1/deadV2 relates to our transfer/re-transfer scheme.

Our switchgear transfers via open-transition and re-transfers via closed transition.

Thank you and hope there are also GE folks here.

 

[nightfox1925]

Thank you very much for all your contribution. I am actually reviewing the transfer and re-transfer logic programmed inside the C60 relay and I'll keep everybody posted.

By the way, this seems to be an awfully dumb question but I will go on with it anyways just to clear my head:

What do you mean by Phase Undervoltage Dropout on undervoltage relay terms? I know what U/V pickup means but how about this?

 

[slavag]

Hi Nightfox.
The same terms. You use U/V pickup term, it's more North American term, in IEC world we more use term U/V start or IEC symbol U< or U<< start.
BTW, C60 for LV board? Why not some smart relay or small PLC? I'm not against, intresting why.
Best Regards.
Slava

 

[nightfox1925]

Hi slavag, for some awkward reasons, the client specs specified it. I know this C60 is for Bay Controllers but that is how ridiculous things are sometimes being done on this part of this world.

 

[slavag]

OK.why I asked, becouse we provide now design of changeover system for LV board with MV bay controller too. Instead PLC/UV relays/synchrocheck relays, etc. .
I see, not only we, is good .
Good Luck.
Slava

 

[nightfox1925]

Slavag, I got an update as to the why?

The C60 controller (IED) is a PLC wherein the synchronization and the transfer/re-transfer scheme can be programmed into a logic inherent to the relay. This will in turn, saves cost of wiring, interposing relays, U/V relays etc.

 

[nightfox1925]

Hi slavag,

I have read through a spec from the client.

It states that the transfer will occur if the voltage drops to 85% Nominal (0.85 P.U.) with a time delay of 3 seconds. The voltage on the other bus should be >90% nominal to allow transfer.

I don't think 3 seconds is enough to dissipate LV motor starting. However, I taking plans to determine the starting time of the highest rated motor connected to this 600V switchgear to verify whether the U/V time delay is sufficient or not.

Does this mean that the U/V element (in the G.E. lingo: AUX U/V OP) connected to the bus PTs should be set at 90% nominal (0.9 P.U.) and have this BUs U/V element block the transfer?

The other settings will be:

Synch Dead Maximum Voltage: 0.25 P.U.

Synch Live Minimum Voltage: 0.75 P.U.

By the way, I forgot to inform that V1 and V2 are voltage on the sources and are connected to the line PTs. The bus PTs are connected to the C60 relay's Auxiliary Voltage input.

 

[slavag]

Hi Nightfox.
"It states that the transfer will occur if the voltage drops to 85% Nominal (0.85 P.U.) with a time delay of 3 seconds. The voltage on the other bus should be >90% nominal to allow transfer."

From our expirience 0.85Un for 3 sec it's very sensetive setting. From other hand, maybe is OK.
What is a very importanr point: are you client have re-start system for the motors? For example in our project, we have finished transfer in 1.5sec max, after 2sec...I have found new country for living .

"Does this mean that the U/V element (in the G.E. lingo: AUX U/V OP) connected to the bus PTs should be set at 90% nominal (0.9 P.U.) and have this BUs U/V element block the transfer?"
Yep, you are right, we used term "normal voltage".
setting for the LIVE and DEAD for my pinion is best choice, from time to time we use 0.3Un.

Connection is OK. additional Q's what is a procedure of your transfer, As I understand it's break before make, but what do you block with "fault voltage" on the second BB, break or make?
Best Regards.
Slava

 

[nightfox1925]

The transfer procedures are as follows:

Manual Transfer - Closed Transition
1. Initial conditions: 52-1, 52-2 closed, 52-3 open
2. Select "Trip 52-1"
3. Close 52-3, synch check verifies, logic checks for any
transfer blocks, protection blocks etc.
4. 52-3 closes, 52-1 instantaneously trips.

Manual Re-Transfer - Closed Transition

1. Initial conditions: 52-1 open, 52-2 closed, 52-3 closed
2. Select "Trip 52-3"
3. Close 52-1, synch check verifies, logic checks for any
transfer blocks, protection blocks etc.
4. 52-1 closes, 52-3 instantaneously trips.

Auto-Transfer - Open Transition

1. Initial conditions: 52-1, 52-2 closed, 52-3 open
2. Phase line 1 U/V operates (V1<0.85 for 3 seconds)
3. 52-1 trips
4. 52-3 closes

 

[slavag]

Hey. We are in synchronasing .
"
1. Initial conditions: 52-1, 52-2 closed, 52-3 open
2. Phase line 1 U/V operates (V1<0.85 for 3 seconds)
3. 52-1 trips
4. 52-3 closes
"
We provide point 3 only in case of "noraml volatge" ( part of 52-3 ready, no trip, truck inserted, control voltage OK, no protection trip and BB voltage OK)
Regards.
Slava

 

[nightfox1925]

Thanks slavag,

One thing more, if the 27 pickup is set at 3 seconds before it will start initiating an open transition transfer, what will be a typical total time delay being set before it initiates 52-3 to close?

On closed transition transfer, if 52-1, 52-2 and 52-3 are closed, what would be an typical time delay to be set before the bus tie (52-3) trips open?

 

[nightfox1925]

To all,

How much time will it take for a residual voltage to dissipate?

 

[waross]

The decay of residual voltage from motors depends mostly on how fast they slow down. It depends to a lessor extent on motor design and the connection of capacitors. Many motors will have lw enough residual to reconnect after 5 to 10 seconds.
BUT, there are serious exceptions. For example, in a sawmill, large motors driving high inertia loads such as band mills, chippers, or hogs, and having capacitors connected to the motor leads can still have dangerous residual voltages after a minute or more if they are left to run down on their own without some type of braking.
If the motor contactors are opened, you may transfer safely but do not attempt to restart the motors until the residual voltage has dropped to a safe level.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[slavag]

Hi Nightfox.
Possible a few options.
1. Residual voltage connection.
52-1 opened status--Bus voltage below 0.4Un ( for example, we have boards with 0.5Un)-->52-3 close command.
Of course you need check restart current of all motors for avoid ins. overcurrent trip, or provide some load shedding.
2. Residual current connection with motor contactor status
52-1 opened status--Bus voltage below setting--all motor contactors are openeed----> 52-3 close command
In case of 1 and 2 you dont need any timer for 52-3 close command
3. Long time close command---after 10sec, for example, you don't check ( only 52-1 opened status) voltages---> 52-3 close command, it's special case, but used.
As Bill saied, residual voltage decay time on the motor bus it's very dependly value. up tp 10sec or more, if it's number of fans.
Becouse this, you need continusly monitoring of residual voltage and not timer.
Hope that help.
Best Regards.
Slava