Chapter Seven, breaker control and auto reclosing. There are a number of basic requirements for circuit breakers which are desirable in their control circuits. control of the CRO of the closing, control of the tripping, Chip free, anti pump and reliabilities. These features can be found in motor solenoid spring stored energy and pneumatically operated breakers. Let's take a closer look at these features. When we initiate a trip stroke, it means that a signal must be provided to trip the breaker.

This may involve energizing a solenoid coil to trip a latch or In the case of air blast breakers to admit air to the blast valves and contacts. initiating a trip Stokes stroke also involves initiating other things to happen during the tripping of the breakers such as anti pump, etc, etc. We'll, we'll talk a bit about those in a few minutes. Cut off is a means of automatically disconnecting the trip coil once a trip signal is sent, primarily because you don't want to keep the trip coil energize because it could heat up and burn out but also, a lot of automatic things could happen once a trip signal is sent. There could be an auto reclose coming close on the heels of the trip signal and if if, if the control mechanism to trip the breaker is manually operated by an operator, chances are he's gonna hold that trip signal in a little bit longer than required.

Could cause the breaker to trip again if it was automatically re closed. So anyway, once a trip signal is sent to the trip coil, there's a cut off that automatically disconnects the trip coil from from the initial trip being sent. The trip free function when it closed when closing a breaker the closing device for example, a solenoid in a solenoid operated breaker is energized and the plunger operates through the linkage to close the breaker contacts. At the end of the closing stroke appreciable time is required to de energize the solenoid coil. In the event that the breaker has been closed on a faulted circuit it must be reopened as quickly as possible. If a breaker can trip automatically, upon receiving a trip signal before the closing operation is complete.

It is said to be Trip free. Various arrangements are provided to obtain trip reaction. solenoid operated breakers are sometimes provided with a collapsible linkage pneumatically operated breakers may be equipped with two latches, one of which is unlatched during normal trip operation, and the other is only unlatch for a trip signal when the breaker is closing. Other breakers use large dump valves to quickly exhaust the air under the closing piston. Many motor operated breakers obtain a fast trip reaction by use of a relay energized from the trip circuit to be to open the closing circuit. These methods would be known as mechanical trip pre pneumatically, trip free and electrically trip free respectively.

Anti pump When a breaker is closed in a trip free operation results, the close and trips stroke will be completed in a very short time. For a modern pneumatically operated high voltage breaker, the complete operation will take less than one half of one second. Thus, it's quite likely that the operator will still have the control switch in the closed position. Means must therefore be provided to prevent the breaker from closing a second time. Even though the operator is holding the control switch in the closed position. This is usually accomplished by the use of a sealed in relay, which can only be released by the opening on cold opening the closing control switch.

When this feature is incorporated in the control circuit, the breaker is said to be pump free or anti pumping following a trip free Operation the break of the breaker the operator must open the control switch before a second attempt to close a breaker can be made. We will be looking at the anti pump circuit to see how it works in a couple of slides. Reliability a circuit breaker is a protective device, it will be called upon to open faulty circuits infrequently However, while it may stand inoperative for a long period of time, it must be relied upon to operate correctly in times of trouble. Reliability for such a protective device is essential. For this reason, and battery supply is always used to provide the tripping power and in most cases the closing power for a breaker. The control circuits usually have a separate trip and close bus.

This is to give extra reliability to the trip circuit on 115 kV and above circuit breakers there's usually dual trip buses, that if a closing control circuit fuse fails, during a closing stroke that trip circuit and or circuits associated with the trip function will not be affected. This is what a typical DC control circuit for a breaker might look like. You'll notice that the closing circuit has a separate fuse supply than the trip circuit. They are independent of each other, yet they control the same breaker. Okay, let's take a closer look at one of these control surface just to see how it works. This is the portion of the closing circuit that is associated with the anti pump logic.

This is the basic anti pump circuit Showing at rest with a breaker open. Notice that relays 52 X and 52 y as well as the breaker closed coil are de energized. Since the breaker is open, the A pally switch is open and the B poly switch is closed. If the breaker is given a close signal say from the operator close control and held on 52 x picks up through 50 to be pally and closes its contacts bringing positive to the breaker close coil. This will close the breaker opening the beat pally and closing the A Polly switches energizing the 52 y at the pump relay. This relay opens it's normally closed contacts 52 ly de energizing and opens the closer cuts to it.

The other 52 why normally closed contact drops out the 5253 x relay. The 52 wire relay seals itself in and remain sealed in as long as the close which is held on this holding of the close which is not necessarily a long time, but if the breaker is feeding a permanent fault the breaker will trip in a fraction of a second. But since the 52 y anti pump relay is sealed in the close signal will not again reach the breaker close coil preventing the pumping action from taking place the breaker remains open. Once the closed switch is released, breaking the positive seal into 52. Then all goes back to normal. In the case of high voltage circuit breaker closures, the protection for the say line protection will immediately upon tripping at the same time initiate an automatic reclose feature which can be selected or D selected by the operator when operating a station either remotely or on site.

The reclose relays themselves that provide the functioning for reclosing the relay are associated with a breaker and there may be two or three breakers associated with the tripping of a line. So, the bridge it's the job of the relays that are associated with a breaker to provide the various checks and balances needed to reclose a line into circuit for example, If we were energizing, if we had one breaker tripped and on either side of the breaker, it's energized but out of synchronism, you certainly don't want to reclose the breaker, it would be the same thing as reclosing into a dead short if it was out of synchronism or if the line you wanted to just check and make sure the line is dead, so you want to have a relay that would check for under voltage conditions before reclosing if there wasn't under voltage then perhaps you wouldn't close the line.

Anyway, the cu h 90 sinker, check reclose relay is an old school relay again, a lot of them are still in service today. And there are they are being replaced by the more modern intelligent electrical devices or IEDs that are coming on the market and we will look at those which are a little bit more compact and a little bit easier to to set up. Hello I thought I would give you a quick look at both. This is no way intended to give you a full blown analysis of the relay. It's simply to give you an introduction as to what it is capable of, and how it's selected by the system. As I said, there are some pre selected conditions involving the BBC cu h 90 really, that are electrically check prior to recloser.

And these items are under voltage of the line plus times and that's usually 10 seconds. In other words, if the line has been tripped, and it's out and it's under voltage for beyond 10 seconds, then this is a selection for reclosing this breaker back into position because the line is dead and you want to energize it. Another more sophisticated way of closing the breaker is To synchro check across the breaker In other words, if you've got voltage or power on both sides of the open breaker, this relay if it is selected for sinker check will actually check the synchronism across the breaker and if it if all three phases are in phase on either side of the breaker, then the breaker or sorry the relay will allow the breaker to reclose sometimes you want to just measure for voltage presence plus time of one second this is a selection that is available.

You can also select a long time by itself for a short time, one of these five selections can be made and this really will provide the intelligence for checking any one of these five items. So, as I said the sinker sinker check supervision is provided to check the voltage That voltage is present first of all on both sides of the open breaker and the two voltage levels are within limits. In other words, they have to be up to at least within a certain percentage of each other and that the phase angle between two voltages remains less than a preset value for a prescribed length of time. The Brahm Bovary synchro check really consists of four main elements. The cu h element, and this is a face checking element which looks at the red to white voltage on each side of the breaker and determines if the phase angle is within a preset value.

The operating range of the element is adjustable from five to 25 degrees and can be modified to operate for a range of 10 to 60 degrees. VG element is a phase angle between two input voltage is measured and if that voltage is 180 degrees or one of the input both voltages are equal to zero, the C u h element remains in a non picked up state. The VGA element is designed to respond to the vector addition of two input voltages v one plus v two. The pa timer element is basically zero to five seconds adjustable DC timer relay which is preset to operate in approximately two seconds with the CH element in neutral position and the VG element picked up the PA timer is is in turn picked up which closes its content Two seconds later to enable a circuit breaker reclose. The P eight relay this element is simply a DC really pick with that picks up when the CH element swings left or right.

If the input voltages are out of phase by a preset angle that co h contacts will close, which in turn supplies positive DC to pick up the PA coil. The normally closed contacts from the PA relay are connected in series with a PA sorry the the PA timer coil which effectively blocks the pickup and prevents a circuit breaker from auto re closing and the this really has two sets of logic circuits. It has an AC side which is connected to the PTS of either side of the breaker. And it has a DC side connected to the battery control circuits and other auxiliary relays which will provide intelligent selecting for the reclosing of the breaker. We're going to look at only a partial bit of the control circuit the DC control circuit which also controls applying the AC qualities to the ch 90 relay. It's certainly by no means a complete set but I thought I would have a peek at just some of the control features that go on.

I had of the automatically reclosing of the breaker. First thing that has to happen In order for autorai closure to happen is there's a selector switch either on a panel or on a remote control system that has to be selected for automatic re closing to be in place. In other words, it has to be selected for auto re close. If it's not selected for auto recalls, nothing will happen. So this switch a lot of times is on a local panel of the operator turns it on, which selects auto Rico's The next thing is that the auto reclose has to be initiated from a protection in this case, it's the line one protection that took the breaker out in the first place. Selecting it or these contacts will actually select for auto re closure again, hoping that the fault will be cleared if say was lightning, it has a chance to clear then the trip relay will automatically initiate a reclose With one of these series of contacts, the other contacts that are in parallel with this with would be from other either line protections or other feeder protections that would initiate a reclose.

In this case, we're only talking about line one protection. The other thing that there are several checks and balances that may or may not be in place, one of them is that the air pressure is good inside the pneumatic circuit that causes the breaker to close. If the air pressure is not there, then reclosing won't be attempted because you can get a partial reclose which would not be good. Then the if all these functions are in place, then the 7963 a relay will pick up and it will seal itself in Once this relay picks up, then it also initiate a pick up of the AC quantities to feed into the ch 90 at VB relay, which is the voltage comparison relays before or as is checking for reclosing. In the AC part of the relay, the 79 a dash l one picks up and caught and connects the AC to the c ch 90 sensing coils.

Before that happens, there is another check that takes place and that is the line disconnect switches. If the line disconnect switches are closed, then it allows re closure to continue. If the disconnect switches open, of course, there's no need to in the Auto reclosing because it won't do anything except close the breaker and you don't need to close the breaker if the disconnect switches open the two voltages on either side of the breaker then energize the AC coils of the ch 90 relay. The VG contacts close when voltage vectors are added to the threshold. If the vector sum of v1 and v2 are zero or 180 degrees out of phase, the VG contacts remain open. The cU cH contacts open.

When phase the phase angle is small closed when the phase angle is large. Pa then picks up opening the normally closed contacts blocking the PA relay. As I said, this is only a partial look at the control circuits for the ch 90. It gives you a partial look at as to the initiation of breaker re closure and applying the AC quantities to the sensing relays and initiating some of the DC timers. What happens in order to give you the under voltage of the line plus 10 seconds time delay or a sinker check or voltage presence plus time and longtime and shortcoming. These functions are all dialed in after the fact and they're provided by the DC circuitry and logic that the ch 90 would be feeding into.

As I said before, the ch 90 relay is definitely an old school really and has a singularity function that is to provide reclosing for the raker a lot of relays now that are coming on the market are almost one stop shopping they are multitask and multi functions and such as the case and I'm only introducing this Schweitzer relay the S l 751. Really, which is providing feeder protection in a way of overcurrent and power flow and you can see all the functions that it does there. One of the things that it does do along with all the protection that it provides isn't that it will provide automatic reclosing and I just want to show you it here that the a lot of the newer IEP type relays that are out there come complete with auto reclosing some of them have single pole tripping or tripping and reclosing Some of them just have the the three pole reclosing this one as you can see it does synchro checks and it does the auto reclosing as well.

So there are other relays out there by as I said by other manufacturers such as Siemens and and the other various companies that produce these, these type of relays and they all usually come complete with auto reclosing attached to it, and it's a lot easier to select the functionality of these newer relays. That ends chapter seven