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86 relay current draw?
5

86 relay current draw?

86 relay current draw?

(OP)
Hello,
I'm troubleshooting a failed trip circuit for an 86 lockout relay. This is a GEI-28712E, similar to an Electroswitch. The 86 coil is tripped by one of several relays. The contacts for one of the relays has been welded closed, and I'm trying to figure out how that could have happened.

There was a standing trip on one of the relays, and the operator didn't know, and he kept trying to reset the 86. He held the 86 in the reset position long enough that it started to smoke. An observer told me he held the switch for at least 5 seconds, trying to get it to reset. I'm pretty sure this is what caused the welded relay contacts.

The current rating of the welded contacts is 30A for 0.2 second, and a continuous rating of 7A (at 125VDC). The trip voltage is 125VDC. The GE manual for the 86 says that at 125VDC, the resistance of the 86 trip coil is 24.3 ohms at 25 degrees C, and that the seal in time is 0.2 seconds. But this doesn't add up with a welded contact that can handle 30A. According to the manual, I could hold the handle to reset as long as I want and I'd never pass 5A.

I'm trying to figure out what the steady state current through that coil would be. If it's just a coil, then after the transient, it's a short circuit. But the manual says 24.3 ohms? Is there a resistor in series with the coil, or is that the impedance of the transient measured at 0.2 seconds?

Thanks for your help
EEPROM

RE: 86 relay current draw?

I am not entirely sure I understand you question. smile

But how many times a relay can go on/off before it welds together is usually shown in a graf like this.

This is from another relay since you didn't say, what the model and number was.



So dependent on how big the effect is over the tung with the highest effect on the relay it will be able to pull and release a specific amount of times before it welds together which it will do sooner or later.
Breaking up DC voltage givs more arc and is harder to turn out, gives relays that handles DC voltage shorter lifespan.

BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

RE: 86 relay current draw?

(OP)
No, this is not addressing the right question. I have a closed relay contact (a standing trip) upstream of an 86 lock out relay. The closed contact is not changing states. The 86 is held in the reset position by an operator, making the trip circuit, which draws current through this closed contact, and through the 86. I would like to know how much current is flowing if you hold the lockout relay in the reset position.

RE: 86 relay current draw?

I don't use those but, In some lockout designs where high speed is required, the coil is rated for 24V, with a resistor inserted on a partial travel of the lockout. This is to allow targeting of older relays.
Thus, if you hold the lockout in the reset position the resistor is never inserted, and the contactor never interrupted.

You will need to refer to the manual for that lockout to be sure.

And the reason I don't use high speed lockouts, is the speed is not worth the complicated circuit. The normal speed is fast enough for me.

RE: 86 relay current draw?

Smoking coil = shorted coil maybe.

RE: 86 relay current draw?

Quote:

The GE manual for the 86 says that at 125VDC, the resistance of the 86 trip coil is 24.3 ohms at 25 degrees C,
Is this when it is pulled?
Because if it had welded together it doesn't mean it was welded together in a fully drawn state as it would have been if it had been pulled and alright.
The welding takes place when the relay tries to pull apart mening that between the tungs there will be a build up of metall keeping the tungs at a distans from each other so when you try to pull it again it's not sure it will be able to do so completely.

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

RE: 86 relay current draw?

(OP)
I don't know what happened, that's what I'm trying to figure out. I don't believe the relay changed states. I just want to know how many amps (approximately) are drawn from an 86 relay when it's forced into the reset position with a standing trip. If that number is 10A, then I don't believe the relay is question could have been damaged or welded. But if the amp draw is 50A, and the operator held the pistol grip for 5 seconds, that's a different story.

I just need a good estimate on what the 86 will draw. I'm guessing that no one posting here knows that.

RE: 86 relay current draw?

Is it possible the initiating relay opened its contacts faster than the 86 internal contacts in the trip circuit? When the 86 operates, these "b" contacts in the 86 should interrupt the trip current. Why didn't the initiating relay trip circuit release the trip on no fault (or similar). Is this by design? SEL relays have a setting called "Unlatch Trip" and can be assigned a number of elements (NOT Trip) for example.

I have an Electroswitch series 24 125VDC in front me and its ~28 ohms.

The attached shows a series 24 LOR with the internal contacts in series with the 86 coil that should interrupt the trip current as the LOR operates. If something is not right for these internal contacts, you can be applying a signal on a device normally rated for intermittent duty continuously.

RE: 86 relay current draw?

(OP)
The pistol grip was physically held in the reset position, that's why the b contacts don't matter. This is a case of an operator not being trained and over-riding the system.

But...now let's talk about that 28 ohms on the coil. 28 ohms is a lot of resistance for a coil. Is that DC ohms or impedance? The resistance is just wire when it's a DC circuit. The coil has an inductive transient, but after that it's a short. If the coil is 28 ohms at steady state, then I could hold the pistol grip in reset all day long and I'd never draw 5 amps. If that's true, then the contacts in question were not damaged by the operator holding the switch in reset. I'm suspecting the coil is drawing more than 5A. A lot more.

That's what I'm trying to figure out. I have an electrician today who's going to put an ammeter on the coil and hold the pistol grip to reset for 1 second and see the amp draw.

RE: 86 relay current draw?

eeprom,

I think thermionic1 is on to something, but it is still a bit puzzling. Older lockout relays can become "sticky" after sitting unoperated for years and if the fault was intermittent the initiating relay might have dropped out before the 86 could operate. I have seen this, but the initiating protective relay contact burned open, not closed. Can you provide a photo of the welded contact?

Also, the smoke is not hard to explain. Lockout relay coils are designed for short energized time. If the voltage is 125 volts and the coil resistance is 24 ohms the power dissipated in the coil is 125x125/24 = 651 watts. The current is 5.2 amps. At over 600 watts dissipation the coil heats up quickly.

RE: 86 relay current draw?

(OP)
I don't have a photo of the welded contact, and I haven't yet confirmed it's welded. I just know it won't change states.

I don't seem to be making my point. The 86 relay trips everything just fine. It's wired right and has been in service for 30 years. The problem occurred when a human being went to reset the lockout while there was a standing trip on one of the protective relays. This action would, of course, result in another trip. Now if the guy holds the pistol grip in the reset position, he's preventing the 86 from tripping. This is allowing current flow. How much is the question.

If it's really 5A, then most likely the relay contact did not get welded and has failed for other reasons. I'm trying to figure out how much current would flow if you held the pistol grip in the reset position. I am not trying to troubleshoot the lockout relay.

RE: 86 relay current draw?

eeprom,

Relax and use Ohm's law, pretty basic stuff.

If you know the applied voltage and the resistance in the circuit the current equals the voltage divided by the resistance. Again, if the coil resistance is about 24 ohms as you said in your original post the current is 125/24 = 5.2 Amps. If your 125 volt system floats at about 132-133 volts as most do the current is about 133/24 = 5.5 amps.


RE: 86 relay current draw?

(OP)
So, the steady state current draw is 5.5 amps. That's what I wanted to verify. I wish I had known of ohm's law before now.

RE: 86 relay current draw?

eeprom,

3 more things:

1) Your lockout relay has been abused. I would be concerned about its future reliability.

2) I would get some training for your operator, understanding of protective device function appears to be needed. LOR tripping is a "call in the experts" situation, not something to try to override.

3) If you need to upgrade your protective relays take a good look at the SEL relays with their patented high interrupting output contacts that can interrupt 10A DC at 125VDC.

Good luck,

RE: 86 relay current draw?

(OP)
MKFPE,
I work at many small plants, and a lack of operator training is a common problem. Very common.

At this point, my only concern is to find out what's wrong with the trip circuit, get it repaired, and to explain to the owner what happened. I don't yet know why the contact failed. Those other items you mentioned have been addressed numerous times in the past.

RE: 86 relay current draw?

It may be a failure of the trip coil. A failure of the economizer circuit or a mechanically jammed trip solenoid.
If the economizer circuit does not operate, the current will be very high. Hold it in and something will smoke.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

RE: 86 relay current draw?

Buy a new lockout. The relay is not meant to see DC for long periods for through the coil. Whatever process you have is more expensive than than another relay. If smoke comes out of anything, you replace it.

RE: 86 relay current draw?

eeprom,
I am almost certain the contact welding is not due to the current rather it is due to arcing. As it was held in Reset position for only 5s, I doubt the current magnitude can cause that much heat to cause contact welding. Mind you, these contacts of 86 are tough and do not melt that easily.
When the operator was holding the pistol switch against the force of the operating coil, I guess there was arcing as the contact tried to open.

RE: 86 relay current draw?

Have you checked that the coil on the 86 is still OK or not? It's pretty easy to do an initial check with an ohmmeter because it should be 24ohms or maybe a bit more.

RE: 86 relay current draw?

(OP)
Gentlemen,
This post has nothing to do with the lockout relay, other than trying to determine the steady state current flow. The lockout and the obvious need for operator training are separate issues and I assure you they will be dealt with. :) Thank you so much for all of your suggestions. I will re-post once I have figured out what happened.

RE: 86 relay current draw?

Another thing is, the older GE lockouts had a problem with becoming sticky, if not torqued to the proper adjustment from time to time. That can cause a welded contact, as the lockout operates too slow.

If you have this type of lockout that requires torqueing, you need a program to check them from time to time.

RE: 86 relay current draw?

Huh, how could figuring out why the contact in the protection relay failed not be about the 86 relay? You asked why the contacts in your protection relay failed. You also posted that it happened after the operator held the 86 until its trip coil started to smoke. The smoking hot temperature of the trip coil could have easily caused the coils of varnished wire to melt together causing a short in the coil, either partial or complete. Those shorted coils could then easily cause a MUCH higher current in the circuit. But hey, why would anyone need to investigate the ACTUAL IN CIRCUIT 86 relay as a possible cause?

RE: 86 relay current draw?

Quote:

This post has nothing to do with the lockout relay, other than trying to determine the steady state current flow.
You may be labouring under a misconception.
May I suggest that determining the normal current may not be as important as determining what the abnormal current may have been?

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

RE: 86 relay current draw?

(OP)
Well, I'll say you guys are persistent....

Here's some measurements from the field. I would love to see someone apply ohm's law to this. Because this makes no sense to me. And the guy doing the measuring is very good. These are accurate measurements.

Measurements on lockout relay....................
Resistance of coil, 2 measurements: 23 ohms, 23.4 ohms. GE manual says coil it should be 24.3
Current through coil during reset, 3 measurements: 14.5A, 10.2A, 7.9A (done in order about 30 seconds apart)
Standing voltage: 132V.
Voltage during resets: 129V.

For a fairly stable voltage, and coil resistance, I got 3 wildly different current measurements.

From the point of view of the failed contact in the exciter, this is not enough current to damage it. So that problem remains unsolved. All I know is that the contact will not change state. I assume it's welded shut.

For the lockout relay, I believe this is what's happening. The insulation is damaged, but it's intact enough that it doesn't show up on a resistance test. When you push current through it, the insulation breaks down enough to allow the current to take multiple paths through the windings; this would explain the higher than expected current. The current causes heating in the coil, raising the resistance of the wire. This could explain why the current measurements go down over time.

The lockout relay need to be replaced, so no need to discuss that. But I would like an opinion on the different current measurements.

RE: 86 relay current draw?

Since I am not a gentleman, I guess I am excluded and will give it another try. smile

This is a manual I found it seem to be old maybe there are newer.

https://npeinc.com/manuals/LV%20breaker%20manuals/...

But from my understanding the coil is to realize the latch when tripping and the reset is mechanical?





So the coil should not be energized at all at a reset. ponder

What makes a contact burn together isn't the amps over it when it is fully closed which are the values you provided max 30 A and continues 7 A.
But the arc that burns between them when opening and closing them and for how long that arc is lit.
And that time gets longer if it closes or opens to slow or if it does not open enough which will happen after a time if a build up from earlier arcs are left unattended or if the power consumer is a coil with a magnet and there is no arc protection over the coil or it is broken like a capacitor, diod, free wheeling diods, or such.



BR A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

RE: 86 relay current draw?

Nothing you posted explains the high current of the first test. Coil heating could explain the current going down during the subsequent tests.

That is showing that datasheet theory doesn't beat actual testing. If the tripping current is really 14.5A on a good 86 relay then that could explain the contact welding, even when the contact is supposed to be rated for switching that level of current.

RE: 86 relay current draw?

Meaning that if the function of the coil is to realize the latch it will be energized as MKFPG sad with 125x125/24 = 651 watts for 0.2 sek 200ms but if you pull it for 5 sekunds it's not made to withstand that, so smoke there will be...

I have had the same problem with a bipolar relay it burns after power outages because there is no compressed air avalibul so the takeover function can not be completed and do not come.

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

RE: 86 relay current draw?

When did the relay contact last attempt to open? I was a bit confused whether the relay contact never changed state because it was welded, or whether the relay never attempted to open the relay contact. The interruption rating of relay contacts is often less than 0.5A @ 125 VDC. If the 86 was already damaged, the relay could have been damaged during a previous operation.

RE: 86 relay current draw?

ponder Totally beside the point..
With 125x125/24 = 651 watts I could heat my car motor in the winter I think the engine preheater is between 550 -750 W thumbsup2 even that will not help when it is -30 C at times.

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

RE: 86 relay current draw?

Star for Bacon. It is unlikely the protective relay contact is rated to interrupt 86 coil current. With the series contacts held closed, protective relay contacts will weld.

We smoked an 86 one day when commissioning. The panel drilling was off a bit, and the shaft rubbed against the hole. The hole was enlarged when the replacement went in, and commissioning proceded.

RE: 86 relay current draw?

This thread and another recent about tripping contacts points out the absolute need to understand the expected operation of very common T&D P&C designs where external clearing contacts allow operating contacts to function flawlessly apparently way outside their ratings. One medium sized utility can have thousands of them. The perform yoeman duty year after year. But abuse them, even a little, and all bets are off.

Do it right and the ratings really don’t matter. Do it wrong and there are no ratings that can make it work. Well established practice.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

RE: 86 relay current draw?

I’ve had these trip coils burn out before. It’s why we have a couple of extra trip coils.
I didn’t read every comment, but was the fault cleared when the guy held the handle to reset for so long?
I really don’t understand why he was holding it so long anyway. If it doesn’t reset either the coil is drawing the latching mechanism or the latching mechanism is broke.

Change the coil, test the 86T, and see what caused it to trip. Forget about trying to figure out how many amps it pulls.
I seriously doubt that’s the issue.

RE: 86 relay current draw?

Hi!

It could be possible that the trip contact of your protection relay is set to latched operation which you might have misconstrued as welded. A simple reset of the protection relay may release the latched trip contact.

Regards.

RE: 86 relay current draw?

>> "I got 3 wildly different current measurements"
Redsnake's excerpt from the manual mentions a capacitor. Decreasing current could be a function of the capacitor charging.

RE: 86 relay current draw?

I was thinking that too, but since no more information or electrical drawings was provided (I am not familiar with this kind of equipment) I didn't point it out.

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

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