600 Amp Meter Base

[mivey]

So if I connect to the top and they connect to the bottom then they can just switch leads if it is wired incorrectly? I thought they were saying that the CT's would have to be removed and turned around.

The source is indeed on the bottom. No need to move the CT's. If it gets reversed wired, you could just swap the red and black voltage leads; probably the easiest point would be at the test block on the left side (don't have a good view of that area to see if they actually land there).

In the normal mode, the CT on the left and the voltage have complimentary fluxes. The current on the right is moving in the opposite direction but the meter is wired for a reversal so that the magnetic flux is additive with the current on the left. Look at the orange and green currents and the black to red voltage. Let's look at normal and reverse wiring:

Normal: When we have a voltage rise from neutral to red (V_L-N), we also have a voltage rise from black to red (V_L-L, right to left terminal: our voltage reference). Current flows from orange to white (top to bottom) and from white to green (bottom to top). The orange current and the voltage have the same sign. The green current has the opposite sign from the voltage but the meter reverses the current so the green flux is additive with the orange flux. Now the currents and voltages have the same sign so the POCO is delivering energy to the customer.

Now reverse the source and load: When we have a voltage rise from neutral to red, we also have a voltage rise from black to red (right to left: our voltage reference). Current flows from white to orange (bottom to top) and from green to white (top to bottom). The orange current and the voltage have the opposite sign. The green current has the same sign as the voltage but the meter reverses the current so the green flux is additive with the orange flux. Now the currents and voltages are different in sign and the meter shows the customer is delivering energy but the customer is actually taking energy. Reversing the red and black voltage leads corrects the error.

Note that the CT current is weighted by 1/2 since we are using L-L voltages instead of L-N voltages.

 

[meternerd]

I've seen these things displayed at many of the utility supply meetings I've attended. Not much interest from anybody so far. It is, as you say, a 4S Class 20 setup. 120/240 3W. Can't read the CT ratio, but it's probably 600:5, so you'd have a 120 multiplier. One problem with these things is that the CT ratio is so high. Small CT's such as this one have a TRF (Thermal Rating Factor) of 1.5, meaning you can only put in 150% of the rated current without overheating the CT. On light loads, there is very little secondary current to the meter, and if a mechanical meter is used, you can get under-metering. A CT with a TRF of 4.0 is a better choice. You can get a 200:5 CT that will meter fine all the way up to 800 A, but still only has a multiplier of 40. Looks like a combination O/H underground panel wired for underground feed. Would I allow one in my district? Nope.

As far as CT wiring goes, H1 is polarity on the primary side and X1 is polarity on the secondary side. Current in H1 means current out X1. Get it reversed and the meter runs backwards. Meters can be ordered so they record +Kwh forward or backward, (detent), forward only (unidirectional) or +Kwh in forward and -Kwh in reverse (net). Socket is meant for current (vertical jaws) to be polarity on top. Voltage of L1 and current of L1 must be on the same side. Ditto for L2.

Now you know why I go by "meternerd". I LOVE this stuff!

 

[Dennis Alwon]

Thanks to all for their input. I rarely use CT's and when I do the power company wires them- I just install the JB and the meter base. This one is new to me and I like it so far. It is much better than the 36x40 box they usually require.

 

[mivey]

I would think for a metering setup they would use CTs with extended accuracy and range beyond ANSI C57.13. I would be interested in seeing a pic of the CT nameplate if Dennis would be so kind.

 

[Dennis Alwon]

I would think for a metering setup they would use CTs with extended accuracy and range beyond ANSI C57.13. I would be interested in seeing a pic of the CT nameplate if Dennis would be so kind.

I didn't take a pic but here is the info

Itron-- I think this may be the ratio 200:5A

Type R6BA

Cat # 92353-050
SN #67576266

.3 80.1 80.2 Those numbers are there above the following info
RF= 3.0 a 30C AWB-- I think it is AWB
RF= 2 a SSC AWB

60HZ 1C:0.6kv
BIL: 10KV

 

[mivey]

I didn't take a pic but here is the info

Itron-- I think this may be the ratio 200:5A

Type R6BA

Cat # 92353-050
SN #67576266

.3 80.1 80.2 Those numbers are there above the following info
RF= 3.0 a 30C AWB-- I think it is AWB
RF= 2 a SSC AWB

60HZ 1C:0.6kv
BIL: 10KV

Left the readers in the truck?

This CT is 0.3% accurate at both 0.1 and 0.2 ohms standard ANSI burdens (.3B0.1B0.2). It can carry 3*200=600 amps at a 30 deg C ambient (3.0@30C). It can carry 2*200=400 amps at a 55 deg C ambient (2@55C). The 55C rating is common for padmount installations and in hot climates.

Since you could get 15 amps of secondary current with 600 amps of primary current, they must use a class 20 meter (CL20) and not a CL10 because the CL10 can only handle 10 amps.

Thanks for the info

 

[mivey]

I think it is AWB

AMB, for ambient.

This CT is 0.3% accurate

FWIW, the 0.3% is for 100% to 300% rated current (up to 200% at 55C ambient). Down to 10% rated current it is allowed 1/2 or 0.6% accuracy although most keep their rated accuracy down to 5% rated current (although no accuracy is guaranteed below 10% rated current). The 0.15% accuracy CTs (E0.2,E0.04) have their accuracies guaranteed down to 5% rated current.

 

[mivey]

The 55C rating is common for padmount installations and in hot climates.

Oops. The 55C is a standard rating and 85C is for high temp applications.

 

[Dennis Alwon]

I had my reading glasses and still couldn't make that out. I should have realized the SSC was 55C. oh well. Thanks for the explanation:thumbsup:

 

[mivey]

I had my reading glasses and still couldn't make that out.

I hear ya. I've got a collection of readers and have started a collection of supplementary magnifying glasses. Recently found a pocket-sized dual lens flip-out about the size of a jeweler's loop at Harbor Freight, now if I can just remember where I put it.

 

[kwired]

Since you could get 15 amps of secondary current with 600 amps of primary current, they must use a class 20 meter (CL20) and not a CL10 because the CL10 can only handle 10 amps.

Thanks for the info

And a POCO may still install the CL10 if they don't expect the load to be there.

A service I am in the process of retiring has exposed CT's near the service drop point of attachment. These CT's are only 200 amp CT's according to marking on them, yet they have been in service for quite a few years, supplying one building with a 400 and 200 amp service switches and a second building is also supplied through them with two 200 amp service switches. But peak demand on the meter from past records was only 27.6 kW on 120/240 single phase.

 

[meternerd]

[Since you could get 15 amps of secondary current with 600 amps of primary current, they must use a class 20 meter (CL20) and not a CL10 because the CL10 can only handle 10 amps.]

I'm not sure you can even buy class 10 meters anymore. Class 20 is standard, which is why a RF 4.0 @ 30C 3.0 @ 55C CT is a good match. Lower ratio for low loads and high current capability for high loads. Makes inventory MUCH smaller. But...they are a bit larger because of the increased core size. Revenue class CT's all have high accuracy.

 

[mivey]

And a POCO may still install the CL10 if they don't expect the load to be there.

Then a 400 amp meter base would have been more appropriate.

 

[mivey]

I'm not sure you can even buy class 10 meters anymore.

Not as common but still available.

 

[kwired]

Then a 400 amp meter base would have been more appropriate.

Well in my example a 200 amp meter base may have been more appropriate. Ever try to land 500 copper in a 200 amp meter base, let alone enter the base with a large enough raceway to pull 500 through?

 

[infinity]

So this is designed for an underground service entrance? Seems strange having the load side going out of the top.

 

[Dennis Alwon]

So this is designed for an underground service entrance? Seems strange having the load side going out of the top.

It makes total sense when you think that they have to bend parallel runs up and around from the bottom along with my 3 sets of 3/0 copper at the bottom. Other than having to come out the top I like the arrangement.