LPCT

1. LPCT How can a single sensor cover such a large range ?

2. What is a LPCT ? • LPCT stands for Low Power Current Transformer, also called electronic CT in 60044-8 standard and the CT catalog AMTED305031 • It’s a matter of “classical” magnetic CT and not based on the Rogowski principle • Contrary to standard CT which burden is the wiring and the input impedance of the relay, The LPCT has it’s burden integrated under the form of a resistor: • It’s output signal is then a voltage proportional to the primary current. For Schneider models we have 22.5mV at the nominal current In

3. The characteristics of a =S= LPCT • The rated primary current: This is the primary side current for which the output voltage is equal to 22.5mv • The extended primary current: “metering” class of precision is maintained until this current value. • The accuracy limit primary current or the accuracy limit factor (ALF): Multiplier of the primary side nominal current for which the rated error value is reached. The CT saturation will occur after this level. The “protection” class of precision is warranted until this point. Noticeable difference, the ALF is from 400 to 500 instead of the usual 10 to 30.

4. The characteristics of a =S= LPCT • Ex: CLP2 Ipn = 100A Ipe = 1250A FLP = 400

5. Connection to Sepam • One CCA670 or CCA671 has to be used instead of one CCA630/634 in order to connect the RJ45 cords coming from the LPCT. • CCA670 : lateral connectors for Sepam series 20 & 40 • CCA671 : radial connectors, for Sepam series 60 & 80. • The LPCT can be used with every Sepam Except the models integrating the transformer differential (T87, M88, G88). • With machine differential (M87, G87) CT & LPCT can Be mixed up.

6. Connection to Sepam • Connecting only one or two LPCT sensors is not allowed and lead to a fall back position (same as if the CCA630 is not present). • The cable is terminated by a RJ45 connector. It directly comes out of the CT and it’s length is 6,5 meters. It cannot be modified (neither shorter nor longer, no extension)

7. Sepam : Modifying the rated current • For the CLP range the plated rated current is 100A for all models. • With Sepam it is possible to modify the operational rated current in order to adapt the measurement range (0.05 or 0.1 à 24In) to the need among these values: In (A) = 25, 50, 100, 125, 133, 200, 250, 320, 400, 500, 630, 666, 1000, 1600, 2000*, 3150*. * Take care to ALP value of 40 et 50kA • 2 operations are needed to make the change: • Select the desired In with SFT2841 (or through front panel use) • Change the micro switches on CCA67x accordingly. Each combination of switches allows 2 In values, The setting done with SFT2841 will determine which one is used (by selection of x1 or x5 gain level in input stage)

8. How does it work? • The output signal of LPCT is adapted by a voltage to bring it back to 25mV pour In • Ex for In = 500 A • ULPCT = 5X22.5 = 112.5mV, A the output of the (1+9)/R3 divisor the voltage is 25mV • Ex for In = 100 A • ULPCT = 1X22.5 = 22.5mV, A the output of the (1+9)/R3 divisor the voltage is 5mV

9. Selection of the gain • According to the set In, the selected gain is x1 ou x5 • For In=100A g = 5 5mV x 5 = 25mV • For In=500A g = 1 25mV x 1 = 25mV • In both case we have 25mV for In at the input of the A/D converter.

10. Secondary side injection • It is possible to test the system by secondary injection by using some accessories: 4: remote test plug connection CCA613, flush mounted on cubicle front face, equipped with a 3 m cable to be connected to the test plug of CCA670/ CCA671 (sub-D 9 broches). (this accessory is optional , the ACE917 can be Directly connected on the CCA670/1) 5 ACE917 injection adapter, 6 Standard injection box.

11. Secondary side injection: ACE917 • It allows to inject currents into the 3 phases. • The injection is done on the 1A or 5A nominal current basis according to selected rated current (do not take care of this mention: )

12. Secondary side injection: ACE917 • The “output calibrator” selector has to be positioned on the same position as the CCA670/1 switches. • Ex: In=100A, 3rd switch ON on CCA670 and “output calibrator” selector on position 3 • Nota: the positions 8 to 12 are equivalent

13. Secondary side injection: ACE917 Example : 3rd switch ON on CCA670 and selector on position 3 • In set as 100A : By injecting 1A Sepam displays 100A By injecting 3A Sepam displays 300A • In set as 500A : By injecting 1A Sepam displays 100A By injecting 3A Sepam displays 300A By injecting 5A Sepam displays 500A It is really needed to inject 5 times more current for The In listed in the right hand side column

14. Secondary side injection: ACE917 • The maximum current the ACE917 can sustain is theoretically the same as what the embedded CCA630 it contains (20A permanently 100A/1s) • However the banana plugs and their welded wires oblige to limit the high currents to the shortest possible time • On another side the voltage excursion being limited to 9V, the maximum current that can be injected/1s in position 8 and above is limited to 70A : (100A in position 8 will not cause any failure but the signal isn’t scaled anymore)

15. Secondary side injection: ACE917 • For rated current below 630/3150A the injection current may be reduced by changing the position of the selector. • The injected current will then generate a signal multiplied by the ratio: In new position / In normal position Example : 3rd switch ON on CCA670 and selector on position 5 The ratio is 200/100 = 2 • In set as 100A : By injecting 1A Sepam displays 200A By injecting 3A Sepam displays 600A