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2.5
CURRENT TRANSFORMERS (CT)
CTs with 1 A or di 5 A secondary rated current must be used for current sensing. The choice of the CTs
performances must ensure a sufficient power and the non-saturation in case of short circuit.
The transformer providing a current that is proportional to the ground current must be connected to terminals from
no. 29 to no. 30 [
Fig. 2.3].
Normally IPR-D uses the "RESIDUAL GROUND CONNECTION" [
When using shielded wires (using the Zero Sequence toroid), if the shield passes through the CT, the conductor
earthing the shield must pass again through the CT window in the opposite direction in order to nullify any
contribution of the shield in the calculation of the current to ground [
a) Cable not shielded
POWER SUPPLY
Observe correct polarity when connecting the CTs to the relay. Each CT should have the same orientation and
the points identifying the magnetic directions must be connected as shown in Fig. 2.3.
2.6
CIRCUIT BREAKER STATUS AND CONTROL CONNECTIONS
Connect the circuit breaker AUX 52a/52b contacts to terminals 23 and 24 to display the circuit breaker status on
IPR-D.
2.7
COMMUNICATION
Thanks to the serial ports, a PC or PLC can make the monitoring and controlling of the relay.
Two-wire RS485 port ⇒ 1 conductors pair transmitting and receiving alternatively is used for the data TX and
The ports CANNOT be used at the same time.
The serial port protocol is a subset of the AEG Modicon Modbus protocol.
For the RS-485 port use shielded, twisted-pair connecting wires to minimize communication errors from
noise.
A suitable type of wire is:
BELDEN#9841 AWG 24 shielded and with an impedance of 120 Ω.
Ground the shield at one point only [
Correct polarity for RS485
The connections are cascade-type and end on the converter. Avoid star or loop connections.
A maximum of 32 relays can be daisy-chained together in parallel mode on a communication channel for a
MAXIMUM DISTANCE OF 1000 METERS.
For increasing the number of relays on a single channel to more than 32 refer to ORION ITALIA.
CURRENT PROTECTION RELAY - IPR-D
LOAD
Figure 2.4 – Cable shield
RX.
Fig. 2.3] to avoid ground loops.
Figure 2.5
Fig. 2.3] to sense ground current.
Fig. 2.4].
b) Cable shielded
POWER SUPPLY
2.4
Chapter 2: Installing
LOAD
grounding
Manual P/N: IPR-D GBM 01/09/2006
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