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Power Products FAQ

Power Products FAQ

When the meter/transducer display will blank after applying control power?

• Verify that the meter/transducer’s line (L) and neutral (N) terminals are receiving the necessary power

What is PT & CT ratio?

When measuring high voltage and high current transformer signals, you use a PT (Potential transformer) and CT (current transformer). The ratios between the primary and secondary rated voltages and rated currents are the PT and CT ratios. For example, if the rated primary current/rated secondary current is 500 A/5 A, the CT ratio is 100. The same holds for PT. If not using a PT or CT, each ratio is 1.

For Example:

PT Primary = 66KV, PT Secondary = 110V Therefore select Vrated = 110V.

PTR = 66KV/110V=600 select.

CT Primary=100A, CT Secondary=1A Therefore select Irated = 1A.

CTR = 100A/1A=100 select in meter.

What happens when the data displayed is inaccurate?

• Check that the correct values have been entered for meter/transducer setup parameters   (CT and PT Rating, System Type).
•  Check meter/transducer voltage input terminals to verify that adequate voltage is present.
•  Check that all CTs and PTs are connected correctly (proper polarity is observed) and that they are energized.

Why does the meter/transducer not communicate with the master device?

• Check to see that the meter/transducer is correctly addressed.
•  Verify that the communication parameters (baud rate, parity bit, stop bit) are matched  with the master device.
•  Verify the communications connections polarity [+] & [-] lines

What to do when an energy pulse LED shows continuously ON or not blinking?

Need to set pulse constant and its unit as per below calculation for 2160-A and MFT.

• For Front Blinking LED, select energy type (i.e.-import/KWh-export/KVARh-Import/KVARh-Export/KVAh/MWh-Import/MWh-Export/MVARh-Import/MVARh -Export/MVAh) as per your requirement using Program mode, from OUTPUT and set the value of constant. But here you can get maximum output pulse frequency (& LED Blinking rate) up to 50 msec. So whenever you are using this feature; you should set the value of Meter-Constant in such a way so it will not cross the limit of 50 ms pulse frequency
• As pulse frequency is 50 msec, i.e. in one second maximum 20 pulses can be obtained, hence in one hour maximum 72000 pulses can be obtained
• Total no of impulses/second can be calculated as below
• (Vrate * Irate * CTR * PTR * Pulse Constant in Wh)/3600 <= 20
• Example: Meter specification
• V rated = 240V, I rated = 5A, CT ratio = 40 and PT ratio = 100,
• Above meter can consume a maximum of 4.8MWatt.
• I.e. For 3600 pulses/KWh [3.6 pulses/Wh], it will generate 4800 pulses/sec as per above equation, [240*5*40*100*3.6/3600 = 4800] so it will not work for the meter as it is more than 20 pulses/sec
• I.e. For 2000 pulses/MWh [0.002 pulses/Wh], it will generate 2.666 pulses/sec as per above equation, [240*5*40*100*0.002/3600 = 2.66] so it will work for the meter as it is less than 20 pulses/sec
• This is for single phase only, in case of three phases, energy will be multiplied by three in 3p4w and hence pulses should be calculated for three phase energy.

How to accuracy test the meter based on Energy Pulse Outputs?

• Follow this procedure to test the kWh accuracy of the meter:
1. Acquire a kWh test set (e.g. ZERA brand).
2. Wire the meter.
3. Power up the meter
4. Use Pulse output (default setting is for kWh pulsing at 3600pulses/KWh).
5. Run test and obtain results. Compare the pulse count to the Wh count on the Zera.
6. This value should be within boundaries specified by the accuracy specifications to which the meter conforms (+/- 0.5%).

What is the significance of four quadrant calculation in energy meter's?

Identification of imported and exported active and reactive energy allows you to monitor energy flow in both directions: delivered from the utility and produced on-site which is ideal for facilities with back-up generators or green power capabilities (for example, solar panels or wind turbines)

What is Maximum Demand (MD)?

In electricity measurement, the phrase “Demand” is used to express average value over a period.
MD is calculated on: for KW / KVA.
MD calculation method: BLOCK / SLIDE.
Interval time for MD calculation: 15 / 30 minutes.
When MD calculation method is SLIDE then need to select Sub Interval time for MD calculation, so in the SLIDE method every selected Sub Interval Time Unit will calculate MD with consideration of previous demands up to Interval time.

Block Interval
The simplest way to calculate demand is to calculate the average over a period based on the meter built-in clock, which is called “Block Interval”. For example, in the chart below the values of demand are 5 (from 08:00 to 08:15), 13.3 (10+10+203 from 08:15 to 08:30), 18.3 (08:30-08:45) and 13.3 (08:45-09:00).

The advantage of this method is its simplicity of calculation and no requirement for external synchronization while the disadvantage is that the results will vary between devices. For example, if another meter will have 5-minute offset in its internal clock the demand in the example above will be 6.6 rather than 5 (from 08:05 to 08:10 and 08:10 to 08:15 the value is 5 and from 08:15 to 08:20 the value is 10, which result 5+5+103=6.6).

Sliding Windows Interval
To detect the maximum demand, calculation is performed for any window over time (the window “slides” over the time). In this way, demand from 08:00 to 08:15 is 5, from 08:05 to 08:20 is 6.7, from 08:10 to 08:25 is 8.3 etc. Using this technique, the peak demand of 20 that occurs from 08:25 to 08:40 is detected.

What happens if recorded demand exceeds contract demand?
If the Maximum Demand (MD) recorded by meter exceeds in a billing period then consumer has to pay penalty charges at a rate of “xx” times of the normal billing charges for the demand exceeded than his contract demand.

Can MFT be used for field programmable input and analogue output?

Yes, MFT measures many instantaneous parameters and any instantaneous parameter can be mapped to any analogue output through mMFT Configuration Software tool.

Bidirectional Instantaneous parameters (measurand) can be mapped to analogue output in MFT?

Yes, MFT is capable of measuring bidirectional quantity and also mapped to analogue output.

For Example : If MFT is measured Active power in range of -3.6KW to +3.6KW. Suppose you mapped this power to 4-20mA DC Analogue output then it work as linear Analogue output 4-20mA in accordance with Active measured power -3.6KW to +3.6KW.

Active power      Analogue output

-3.6KW    —>        4mA

0KW     —>      12mA

3.6KW    —>      20mA

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