Voltage Balance Relay / Switching VT inputs

[RumRunner]

Ok. How do I interlock them though- I mean where do the VTs outputs go when both isolaters are closed?

I can't envision the possibility of N9801/N9802 being closed both at the same time. I think this scenario is moot.

Can you cite an instance where this could occur? Based on your preliminary one line distribution schematic. . . when one of this isolator is closed or open, it would close or open the circuit that energizes either north or south bus.

They are indicated as NC and the other NO. They are both in the same string.
Can't have them tied together via closures on N9802 and N9801.

BTW: Are you one of the design team of this $220 million upgrade in Louisiana by Entergy?
I've read about this project a lot.

Keep us posted-- WOW!!

 

[mbrooke]

I can't envision the possibility of N9801/N9802 being closed both at the same time. I think this scenario is moot.

Can you cite an instance where this could occur? Based on your preliminary one line distribution schematic. . . when one of this isolator is closed or open, it would close or open the circuit that energizes either north or south bus.

They are indicated as NC and the other NO. They are both in the same string.
Can't have them tied together via closures on N9802 and N9801.

BTW: Are you one of the design team of this $220 million upgrade in Louisiana by Entergy?
I've read about this project a lot.

Keep us posted-- WOW!!

That is incorrect, you can have them both tied together when the bus coupler is closed or in this case both breakers N1102 and N1105 are closed. By doing so the bus bars electrically become one, and the interrupters are only left interrupting the voltage drop across the bus bar which is usually only about 100 volts. The whole point of single breaker double busbar is so that you can take any busbar out of service without interrupting any lines, transformers or elements.

 

[RumRunner]

That is incorrect, you can have them both tied together when the bus coupler is closed or in this case both breakers N1102 and N1105 are closed. By doing so the bus bars electrically become one, and the interrupters are only left interrupting the voltage drop across the bus bar which is usually only about 100 volts. The whole point of single breaker double busbar is so that you can take any busbar out of service without interrupting any lines, transformers or elements.

I'm referring to what you claim as isolators N9801 and N9802 (post #19) --not the N1105 and N1102.
I can see that both of these “breakers” could accomplish this.

By some design concept, the contacts of these breakers would close only when the dominant power sources are not available. Notice those normally closed (NC) contacts that would make connection when Module N1102 and Module N1105 are deenergized.

Closing these contacts would make the two buses function as one. The absence of the dominant power (Gen#1) would be supplanted by Gen#3 and AUX 3, so no interruption except for the switch yard crew getting P3301 on line.

 

[mbrooke]

I'm referring to what you claim as isolators N9801 and N9802 (post #19) --not the N1105 and N1102.
I can see that both of these “breakers” could accomplish this.

I know you are referring to isolators N9801 and N9802- however, when when both breaker N1105 and N1102 are closed, the north and south buses are "shorted" together in essence becoming one bus. What ever voltage and phase angle difference that may appear between the north and south bus go away when both breakers N1105 and N1102 are closed.

Due to the lack of voltage and phase angle difference, its possible to close N9802 while N9801 is closed, and then open N9801. At worse case N9801 will be breaking 1500amps at 100 volts. This may melt some arc whiskers (for those that have them), but beside that most disconnects will tolerate it well.


In fact IEC 62271-102 Annex B has a standard on this exact concept. To my knowledge the IEEE does not have this standard, but the manufacturer can give the green light on being able to do it.

By some design concept, the contacts of these breakers would close only when the dominant power sources are not available. Notice those normally closed (NC) contacts that would make connection when Module N1102 and Module N1105 are deenergized.

Under normal conditions N1105 and N1102 are closed, and as seen here each bay is either connected to the north or south bus. During a bus fault or breaker failure, dynamic bus logic is used to only open the breakers connected to the effected bus.

So, if say the south bus had a fault, bus differential would send a trip signal to breakers P3201, P3202, N8503, N9409 and N1102 clearing half the bays only. Everything connected to the north bus would remain energized. Same goes visa-versa for a north bus fault.


The bus trip logic is determined by the position of the isolators. When an isolator closes into a bus, its differential is included into the zone of protection, when an isolater opens differential is excluded from the zone of protection- as BF. An overall static "checkzone" is used in the dynamic differential logic to make it more secure.


There is also a backup involving step distance and associated time delays if the bus protection is unavailable- but the busbar protection and breaker fail philosophy falls outside of the discussion.

Closing these contacts would make the two buses function as one. The absence of the dominant power (Gen#1) would be supplanted by Gen#3 and AUX 3, so no interruption except for the switch yard crew getting P3301 on line.

P3301 can be ignored as it feeds 230kv to another set of busbars.

 

[RumRunner]

I know you are referring to isolators N9801 and N9802- however, when when both breaker N1105 and N1102 are closed, the north and south buses are "shorted" together in essence becoming one bus. What ever voltage and phase angle difference that may appear between the north and south bus go away when both breakers N1105 and N1102 are closed.

So when you say “ I'm incorrect” you are just jumping the gun.
​

Due to the lack of voltage and phase angle difference, its possible to close N9802 while N9801 is closed, and then open N9801. At worse case N9801 will be breaking 1500amps at 100 volts. This may melt some arc whiskers (for those that have them), but beside that most disconnects will tolerate it well.


In fact IEC 62271-102 Annex B has a standard on this exact concept. To my knowledge the IEEE does not have this standard, but the manufacturer can give the green light on being able to do it.

Under normal conditions N1105 and N1102 are closed, and as seen here each bay is either connected to the north or south bus. During a bus fault or breaker failure, dynamic bus logic is used to only open the breakers connected to the effected bus.
So, if say the south bus had a fault, bus differential would send a trip signal to breakers P3201, P3202, N8503, N9409 and N1102 clearing half the bays only. Everything connected to the north bus would remain energized. Same goes visa-versa for a north bus fault.

The bus trip logic is determined by the position of the isolators. When an isolator closes into a bus, its differential is included into the zone of protection, when an isolater opens differential is excluded from the zone of protection- as BF. An overall static "checkzone" is used in the dynamic differential logic to make it more secure.

There is also a backup involving step distance and associated time delays if the bus protection is unavailable- but the busbar protection and breaker fail philosophy falls outside of the discussion.


P3301 can be ignored as it feeds 230kv to another set of busbars.

On top upper left of the drawing it distinctly says “to auto transformer”.

​

N1107 provides a path to the “now deenergized bus bars. The 230 kv that feeds the auto transformer from Gen 3 comes back at 115 kV to match the voltage of the bus bars (which are now off). It is obviously connected to a center tapped transformer.
​

So you can't simply ignore it.


​

And besides nowhere in the drawing indicates that power going through N1107 is “foreign”. It is still coming from the same substation via Gen3 or AUX 3.
​

 

[RumRunner]

On top upper left of the drawing it distinctly says “to auto transformer”.

​

N1107 provides a path to the “now deenergized bus bars. The 230 kv that feeds the auto transformer from Gen 3 comes back at 115 kV to match the voltage of the bus bars (which are now off). It is obviously connected to a center tapped transformer.
​

So you can't simply ignore it.


​

And besides nowhere in the drawing indicates that power going through N1107 is “foreign”. It is still coming from the same substation via Gen3 or AUX 3.
​

"On top upper left" should read "on top upper right."

 

[mbrooke]

On top upper left of the drawing it distinctly says “to auto transformer”.

​

N1107 provides a path to the “now deenergized bus bars. The 230 kv that feeds the auto transformer from Gen 3 comes back at 115 kV to match the voltage of the bus bars (which are now off). It is obviously connected to a center tapped transformer.
​

So you can't simply ignore it.


​

The generator (P3303) goes to a 230 kv busbar not pictured here. Other lines are also connected to the 230kv busbar not pictured. One bay of that 230kv busbar connects to an auto transfomer stepping 230 down to 115kv, and that output goes to N1107.

And besides nowhere in the drawing indicates that power going through N1107 is “foreign”. It is still coming from the same substation via Gen3 or AUX 3.
​

All power can be considered foreign when breakers are opened or the busbars are not "coupled" together. As long as both N1105 and N1102 are closed then any set of isolaters can close simultaneously. Normally you have something like this instead:

 

[RumRunner]

The generator (P3303) goes to a 230 kv busbar not pictured here. Other lines are also connected to the 230kv busbar not pictured. One bay of that 230kv busbar connects to an auto transfomer stepping 230 down to 115kv, and that output goes to N1107.


All power can be considered foreign when breakers are opened or the busbars are not "coupled" together. As long as both N1105 and N1102 are closed then any set of isolaters can close simultaneously. Normally you have something like this instead:

OK, there is really no new info from your post. You are simply restating what I've already said. (see post 24)

Honestly, I'm still apprehensive when you said that N9801 and N9802 could be closed simultaneously at some instance based on the PLC command. You could have them both open but not both closed because N1102 and N1105 would be able to handle this part safely.


​

Since there is a clear and undisputed procedure to accomplish this (shorting the buses to act like one) on N1102 and N1105, what would be the compelling reason to do this on N9801 and N9802 ?

​

There would be no arcing or melting of arc whiskers (as you mentioned) when using the N1102 ans N1105 scheme.


​

A lot of this questionable dictum (yours especially) could have some cogency if you can present the ones that are not shown on the drawing. Absence of these data will only lead to wild guesses.

​

I tried to dig through their Entergy website but nothing leads me to LO285501. This is a proprietary document for bidding purposes and I'm not privy to this document.


​

I really hate to go through the aggregate schematic diagram in your post for the simply reason that incorporating this as an addendum to an already designed system would violate engineering protocols. . . we don't know what the chief designer has in his mind.


​

What I'm particularly interested in, is the continuation of the drawing #LO285501 that shows the separate bus that you are talking about.​

If you can locate it without hassle and without the need of divine or magical intervention, kindly post it here.
​

I'm not a magician which I wish I am.
​

 

[mbrooke]

OK, there is really no new info from your post. You are simply restating what I've already said. (see post 24)

Honestly, I'm still apprehensive when you said that N9801 and N9802 could be closed simultaneously at some instance based on the PLC command. You could have them both open but not both closed because N1102 and N1105 would be able to handle this part safely.

Since there is a clear and undisputed procedure to accomplish this (shorting the buses to act like one) on N1102 and N1105, what would be the compelling reason to do this on N9801 and N9802 ?

​

There would be no arcing or melting of arc whiskers (as you mentioned) when using the N1102 ans N1105 scheme.


​

I know I am repeating some information- but precisely due to your apprehension of closing both N9801 and N9802. By not being able to close both isolaters, outages would have be to be scheduled for two transmission lines and one generator for any bus maintenance. For example, breakers N9803, P3101, N9403, would need to be opened, then isolaters change to the south bus, and then closed back in. Once work is completed the same procedure would have to be done to transfer those bays back to the North bus. Two outages on 3 elements when by closing isolaters at the same time it can be eliminated. Right there is the major function of single breaker double bus bar.

​

A lot of this questionable dictum (yours especially) could have some cogency if you can present the ones that are not shown on the drawing. Absence of these data will only lead to wild guesses.

​

I tried to dig through their Entergy website but nothing leads me to LO285501. This is a proprietary document for bidding purposes and I'm not privy to this document.


​

I really hate to go through the aggregate schematic diagram in your post for the simply reason that incorporating this as an addendum to an already designed system would violate engineering protocols. . . we don't know what the chief designer has in his mind.


​

What I'm particularly interested in, is the continuation of the drawing #LO285501 that shows the separate bus that you are talking about.​

If you can locate it without hassle and without the need of divine or magical intervention, kindly post it here.
​

I'm not a magician which I wish I am.
​

The 230kv breaker and a half busbar has no bearing- it can be ignored. I think you are fixated on this particular diagram- I can understand- however view it as a mere example. My discussion holds relevant to any single breaker double busbar substation to which there are many.

 

[mbrooke]

MBrooke...

I'm against a manual-override in this situation. Think more about the inherent-logic available in mechanically-interlocked devices such as an ATC, ATS, or even a reversing motor controller!

Phil

I here you and I do agree. With an SEL421, its possible to set bay control logic such that an isolator can not open if it were irrupt to full current + full voltage, or close into a set of uncoupled bus bars (bus coupler open). Logic here is a good idea.

 

[mbrooke]

You could have them both open but not both closed because N1102 and N1105 would be able to handle this part safely.


​

Ok, I hear you and to quell you fears I give you this:

 

[mbrooke]

Here is ABB's definition- time ran out to edit the above post.

http://ask.abb.com/products/___/dis...bus-transfer-currrent-switching-capabili/1341


Also see page 8:


https://pure.tue.nl/ws/files/2370686/200410772.pdf

Bus-transfer is loop switching between busbars within a substation. Gas insulated disconnectors are those associated with gas insulated switchgear or GIS as it is commonly known.

The loops formed by such switchgear are short compared to those found in air insulated
switchgear arrangements and hence the lower recovery or bus-transfer voltages.
In North America, the term disconnecting or disconnect switch is used instead of disconnec-
tor. Such a device is defined by the Institut
e of Electrical and Electronic Engineers (IEEE)
as:
2
“A mechanical switching device used for changing the connections in a circuit, or for
isolating a circuit or equipmen
t from the source of power.
NOTE: It is required to carry normal load current continuously and also abnormal or
short-circuit currents for intervals as specified. It is also required to open or close circuits
when negligible current is broken or made, or when no significant change in the voltage
across the terminals of each of the switch poles occurs.”
The definitions are very similar
both recognizing an ability to break negligible current. Only
IEC, however, states specific values: up to 0.5 A of capacitive charging current and, for spe-
cific disconnectors, a bus-transfer ability of
1600 A against open-circuit voltages of 100 V to
300 V (Annex B of reference 1).
An earlier version of an IEEE standard included the following note:
3
“A disconnecting switch and a horn-gap switch have no interrupting rating. However, it is
recognized that they may be required to inte
rrupt the charging current of adjacent buses,
supports and bushings. Under certain conditions, they may interrupt other relatively low
currents, such as:
1.
Transformer magnetizing current.
2.
Charging currents of lines depending on length, voltage, insulation and other local
conditions.
3.
Small load currents.”
Horn-gap disconnectors generally have wider phas
e spacings. The implication is that such are
used to break currents and that some accommodation should be made for the reach of the arc
towards other phases or grounded structures. In
fact, this note recognizes that disconnectors
are commonly used in North America to break small capacitive currents, transformer mag-
netizing currents and loop currents. The standard was originally an American National Stan-
dards Institute (ANSI) standard and was revised in 1992 to become an IEEE standard. At that
time, the above-discussed note was removed. The reason for this was that a guide on current
interruption had been developed
4
. The guide was based on the work of Andrews et al
5
and
Peelo.
6
For reasons discussed later in sections 3 and 5 and Annex E, the guide should be
viewed as questionable.

This is for GIS, but explains it in detail and remains similar for open air bus work:


https://www.google.com/url?sa=t&rct...25846187.pdf&usg=AOvVaw0_QcuuMkrj26MouqO5mby0

 

[Phil Corso]

MBrooke...

You approach is too complicated ! You failed to pick up my reference to a mechanically-interlocked contactor (in my day, ANSI 9R, based on EM relays) ! Then, N-bus VT and S-Bus VT become the two 3-ph inputs to the '9R' ! Their coil inputs will come from the '60' ! Furthermore, if the N Bus and S-bus are coupled, one-side (or the other) of the '9R' remains energized, providing voltage to the line's VT-associated circuitry, even when both isolators are closed !

If you are into digital, SEL-700 should work!

Regards, Phil

 

[mbrooke]

MBrooke...

You approach is too complicated ! You failed to pick up my reference to a mechanically-interlocked contactor (in my day, ANSI 9R, based on EM relays) ! Then, N-bus VT and S-Bus VT become the two 3-ph inputs to the '9R' ! Their coil inputs will come from the '60' ! Furthermore, if the N Bus and S-bus are coupled, one-side (or the other) of the '9R' remains energized, providing voltage to the line's VT-associated circuitry, even when both isolators are closed !

If you are into digital, SEL-700 should work!

Regards, Phil

I like this- but one request- can you draw out the diagram? :angel:

 

[Phil Corso]

MBrooke...

Reur #34... Certainly! Contact me via MHF Notification Service!

Phil

 

[mbrooke]

MBrooke...

Reur #34... Certainly! Contact me via MHF Notification Service!

Phil

Email sent- let me know if it came through.

 

[Phil Corso]

MBrooke...

Have previous commitments! Response will be sent later this morning!

Phil

 

[Phil Corso]

MBrooke...

It's on its way!

Phil

 

[mbrooke]

Thanks.


I do have one solution that may not require external switching, ABB relays seem to accept two inputs in addition to a bay VT used in sync check.