battery chargers, NETA, and NERC

[stevenal]

Anyone have access to the '07 NETA maintenance testing spec? The free download frequency chart shows a charger electrical inspection/test in the last column. Can anyone state the nature of this inspection/test? Does it compare to the proposed PRC-005-2 which requires a full current and current limiting test? Thanks.

 

[Zogzog]

7.18.2 Direct-Current Systems, Chargers
* Optional
Page 168
ANSI/NETA MTS-2007
1. Visual and Mechanical Inspection
1. Inspect for physical and mechanical condition.
2. Inspect anchorage, alignment, and grounding.
3. Prior to cleaning the unit, perform as-found tests.
4. Clean the unit.
5. Inspect all bolted electrical connections for high resistance using one of the following methods:
1. Use of a low-resistance ohmmeter in accordance with Section 7.18.2.2.
2. Verify tightness of accessible bolted electrical connections by calibrated torque-wrench
method in accordance with manufacturer’s published data or Table 100.12.
3. Perform a thermographic survey under load in accordance with Section 9.
6. Inspect filter and tank capacitors.
7. Verify operation of cooling fans. Clean filters if provided.
8. Perform as-left tests.
2. Electrical Tests
1. Perform resistance measurements through all bolted connections with a low-resistance
ohmmeter, if applicable, in accordance with Section 7.18.2.1.
2. Verify float voltage, equalize voltage, and high-voltage shutdown settings.
3. Verify current limit.
4. Verify correct load sharing (parallel chargers).
5. Verify calibration of meters in accordance with Section 7.11.
6. Verify operation of alarms.
7. Measure and record input and output voltage and current.
8. Measure and record ac ripple current and/or voltage imposed on battery.
*9. Perform full load testing of charger.

 

[stevenal]

Thanks. No details on how a full load test or current limit test is performed?

 

[oldfieldguy]

Last time I performed a set of full tests on a battery charger was some years ag.

Witht he batteries disconnected and using a resistive load bank of appropriate rating, increase current until nominal full load is reached and monitor voltage and waveform.

For current limit, increase load until the published current limiting range is reached and see that voltage drops off to limit current to the nominal value.

These two tests satisfied the client. The NETA specification says "verify". I am unfamiliar with NERC or other specifications that may go into greater detail.

You should be able to get a testing contractor (that was me) or a battery specialty company to perform these tests if you lack the equipment, the expertise or the desire to do them with you in-house resources.

old field guy

 

[dpc]

I've seen it done with a resistor load bank, as oldfieldguy indicates.

Much easier to load test the charger than the battery itself.

You might check with BPA. I'm pretty sure they no longer do battery load testing at substations, but not sure about the chargers.



David Castor

http://www.cvoes.com

 

[stevenal]

Thanks old guy and dpc. NERC also fails to provide detail.

http://www.nerc.com/docs/standards/sar/PRC-005-2_PSMTSDT_Draft1_2009July23.pdf

With the battery disconnected, most of the filtering is gone. No concern that the microprocessors controlling modern chargers would be damaged by excessive ripple?

 

[dpc]

Steve,

I'm not aware of any problems related to that, but I can see where you are coming from. Wouldn't hurt to check with charge manufacturer.



David Castor

http://www.cvoes.com

 

[oldfieldguy]

Some chargers are filtered well, some are less so. Some chargers do not mind being open-circuited on the output. Some will not handle it well.

I connected my load bank to the charger output first, then turned on the charger. On many modern chargers you can monitor a "ramp" function at this time as it raises output voltage into the load.

You really need to have a good understanding of the features of your particular charger and how they are implemented in order to evaluate performance.

If the charger is a pretty big deal in your operation (and most are) you might want to consider consulting with the manufacturer on commissioning tests. However, these are often actually conducted by a local or regional vendor's "technicians" and sometimes their knowledge is spotty, to say the least.

I guess I'm cynical, but I find it particularly irksome to pay of a "technician" to come to my site, read out of the manual, and try to perform tests with limited understanding.

(Yeah, I've been burnt)

old field guy