IEEE Std. C37.102-2006 tripping 63T same as 87T

[odlanor]

4.9.2.2 Tripping modes
Both the unit transformer and the UAT fault pressure relays should be connected to lockout relays that are separate from the lockout relays connected to the differentials. In some system configurations, these lockout relays trip the main generator and field and/or exciter breakers, trip the prime mover, and transfer the unit auxiliaries. However, if the UAT has a breaker to isolate it from the generator bus, then that breaker may be tripped and the unit auxiliaries transferred without affecting the generator or field and exciter breakers or tripping the prime mover. See the cautionary advice in 4.5.1.4.

Why lockout relays of 63T are separate from the lockout relays of 87T ?

 

[mgtrp]

The differential element and the pressure relay to some extent detect the same faults. Therefore, it makes sense that they use different trip paths, as this increases the degree of redundancy in the protection system.

 

[vandal06]

Do people actually specify separate 86 lockouts for each device? I've not seen it.

 

[collies99]

Transformer typically has 1 lockout (86) Relay, unless There Is a redundant protection set, then each set would have one. Lockout use are for station type faults performing block closing functions on breakers to allow Equipment inspection before re-energization, as well as breaker tripping and other control functions.

 

[jghrist]

I think you could achieve nearly the same reliability by having the 87T directly trip breakers in addition to tripping the 86T. If the 86T failed, the breakers would still trip, but someone could manually reclose them.

 

[odlanor]

jghrist,
By Std lockout relay make both actions: tripping and blocking

 

[Madman4q]

Where I work, our philosophy is to use 2 seperate lockouts.The 63 will hit an '86-63T' and the 87T will hit an 86T. As jghrist stated..At our higer voltages we hit each of the 2 breaker trip coils with seperate 87T relay outputs (SEL 387, moving to 487E)and another relay output hits the 86T which will hit the same 2 trip coils and block close. The 63 will hit the '86-63' and then same trip coils and block close. Contacts from the 63 and '86-63' are brought back in to the relay for data recording. Most of the newer transformers I've worked with (manufactured in mid 90's and newer, ABB and Wauk. 120MVA, 33MVA) it pretty standard to come with just one 86 and thats the '86-63'located in the transformer cabinet. When we do out protection packages we install the 87T and 86T in our relay rooms.
So what are the benefits to us? - We may wrap the primary or secondary lines or both in the 87T zone (not all the time) and 87T fault can be very different from a rapid pressure.
Also these things tend to occur like 1-2AM, so we would get a call from a non electrical operations person..'hey the '86-63' tripped' etc... But, I'm a rookie....

 

[odlanor]

Madman4q
...Also these things trend to Occur like 1-2AM, so we would get a call from a non electrical person operations .. 'hey the '86-63' tripped 'etc ...

I think the latter reason the most convincing!

 

[bacon4life]

In section 4.5.1.4 the standard discusses the possibility of resynchronizing the unit quickly if it can be transferred to a different GSU or UAT. Thus it seems reasonable that the differentials referred to in 4.9.2.2 are an 87O or an 87T that includes both a GSU and a UAT. This section is simply suggesting locking out the smallest amount of equipment possible and does not address relay targeting or redundancy.

Rather than a separate lockout, our sudden pressure relays hit a Qualitrol 909 seal-in relay to provide the targeting Madman correctly points out is very important.

If the desire for redundancy is high enough to justify dual lockouts, then it could be worth considering dual sudden pressure relays as well. We do not use redundant paths for pressure relays, however for microprocessor relays we usually dual trip as jghrist described.

 

[odlanor]

bacon4life,
refers to Figure 7-1a—Unit generator-transformer configuration AND Figure 7-1b—Unit generator-transformer configuration dc tripping logic
Why in Figure 7-1.b 87T trips 86T1 and 63 trips 86T2 , both with same goals?
For me, the only explanation is suggested by Madman4q.

 

[bacon4life]

Yep, the 7-1b sure does show both lockouts. I am unclear why you would combine both the 63-GSU and the 63-UAT trip into one lockout if the goal is to clearly identify the individual problem component for the operator.

The c37.102 introduction states:
The protection philosophy, practices, and limits are essentially identical [with a multi-functional microprocessor based protection system] to those of the implementation using discrete component relays.

Given this starting point, I can see why the newest version has the same diagram as the 1995 version. My philosophy regarding redundancy and the practice of cross tripping of dual trip coils has evolved significantly with the advent of microprocessor based relays. Perhaps the 2018 revision will include guidance on using multiple output contacts from digital relays.

 

[odlanor]

based on the viewpoint of rrr this is my interpretation:
86T1, 86T2 , 86T3 tripping same circuit breakers and shutdown same prime move.
86T1 by electrical system maintenance team.
86T2 by non electrical maintenance team
86T3 by elctrical power house maintenance team.