14.3 Repair instruction IP8767-1 v1M11764-2 v2Never disconnect the secondary connection of a current transformercircuit without short-circuiting the transformer’s secondarywinding. Operating a current transformer with the secondarywinding open will cause a massive potential build up that maydamage the transformer and may cause injuries to humans.Never connect or disconnect a wire and/or a connector to or from aIED during normal service. Hazardous voltages and currents arepresent that may be lethal. Operation may be disrupted and IED andmeasuring circuitry may be damaged.M11764-10 v1An alternative is to open the IED and send only the faulty circuit board to ABB forrepair. When a printed circuit board is sent to ABB, it must always be placed in ametallic, ESD-proof, protection bag. The user can also purchase separatereplacement modules.Strictly follow the company and country safety regulations.M11766-4 v2Most electronic components are sensitive to electrostatic discharge and latentdamage may occur. Please observe usual procedures for handling electronics andalso use an ESD wrist strap. A semi-conducting layer must be placed on theworkbench and connected to earth.Disassemble and reassemble the IED accordingly:1. Switch off the dc supply.2. Short-circuit the current transformers and disconnect all current and voltageconnections from the IED.3. Disconnect all signal wires by removing the female connectors.4. Disconnect the optical fibers.5. Unscrew the main back plate of the IED.6. If the transformer module is to be changed:• Remove the IED from the panel if necessary.• Remove the rear plate of the IED.• Remove the front plate.• Remove the screws of the transformer input module, both front and rear.7. Pull out the faulty module.8. Check that the new module has a correct identity number.9. Check that the springs on the card rail are connected to the correspondingmetallic area on the circuit board when the new module is inserted.10. Reassemble the IED.1MRK 505 378-UEN A Section 14TroubleshootingLine differential protection RED670 2.2 IEC 289Commissioning manual
