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MiCOM P632
Communication Interfaces
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MiCOM P632
Communication Interfaces
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The communication interfaces are provided as a permanent connection of the device to a control system for substations or to a central substation unit. Depending on the type, communication interface 1 on the device is connected either by a special fiber-optic connector or an RS 485 interface with twisted pair copper wires. Communication interface 2 is only available as an RS 485 interface.
The selection and assembly of a properly cut fiber-optic connecting cable requires special knowledge and expertise and is therefore not covered in this operating manual.
WARNING
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The fiber-optic interface may only be connected or disconnected when the supply voltage for the device is shut off. |
An RS 485 data transmission link between a master and several slave devices can be established by using the optional communication interface. The communication master could be, for instance, a central control station. Devices linked to the communication master, e.g. P632, are set-up as slave devices.
The RS 485 interface available on the P632 was designed so that data transfer in a full duplex transmission mode is possible using a 4-wire data link between devices. Data transfer between devices using the RS 485 interface is set up only for a half duplex transmission mode. To connect the RS 485 communication interface the following must be observed:
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Only twisted pair shielded cables must be used, that are common in telecommunication installations. |
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At least one symmetrical twisted pair of wires is necessary. |
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Conductor insulation and shielding must only be removed from the core in the immediate vicinity of the terminal strips and connected according to national standards. |
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All shielding must be connected to an effective protective ground surface at both ends. |
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Unused conductors must all be grounded at one end. |
A 4‑wire data link as an alternative to a 2-wire communications link is also possible. A cable with two symmetrical twisted pair wires is required for a 4-wire data link. A 2-wire data link is shown in Fig. 5-11, and a 4-wire data link is shown in Fig. 5-12 as an example for channel 2 on the communication module. The same is valid if channel 1 on the communication module is available as a RS 485 interface.
2-wire data link:
The transmitter must be bridged with the receiver on all devices equipped electrically with a full duplex communication interface, e.g. the P632. The two devices situated at either far end must have a 200 to 220 Ω resistor installed to terminate the data transmission conductor. In MiCOM Px3x devices, and also in the P632, a 220 Ω resistor is integrated into the RS 485 interface hardware and can be connected with a wire jumper. An external resistor is therefore not necessary.
4-wire data link:
Transmitter and receiver must be bridged in the device situated on one far end of the data transmission conductor. The receivers of slave devices, that have an electrically full-duplex communication interface as part of their electrical system, e.g. the P632, are connected to the transmitter of the communication master device, and the transmitters of slave devices are connected to the receiver of the master device. Devices equipped electrically with only a half duplex RS 485 communication interface are connected to the transmitter of the communication master device. The last device in line (master or slave device) on the data transmission conductor must have the transmitter and receiver terminated with a 200 to 220 Ω resistor each. In MiCOM Px3x devices, and also in the P632, a 220 Ω resistor is integrated into the RS 485 interface hardware and can be connected with a wire jumper. An external resistor is therefore not necessary. The second resistor must be connected externally to the device (resistor order number see Chapter “Accessories and Spare Parts”).
