The P991 Test Block, designed as part of the MiCOM range, offers safe and configurable facilities for monitoring and secondary injection testing in any power system protection scheme when used with the P992 multi-finger Test Plug. A single-finger test plug is also available (type P993) that provides a safe and isolated means solely for the verification of CT circuits.

The P991 Test Block features visible automatic line CT shorting prior to the relay CT circuit being broken on insertion of a P992 multi-finger Test Plug. Up to three stages of sequential contact operation are provided by the P991 Test Plug. To avoid accidental tripping an extraction stop facility is included.

Basic description:

• Provides monitoring and secondary injection test facilities
• Mounted next to the protection relay - convenient 4U rack height
• Monitors up to 14 circuits, each with a specific cassette to configure the action
• Cassettes available for CT shorting, and staged-break and make operation when inserting and withdrawing the test plug

Key benefits:

• No need to disturb protection relay wiring when injection testing or troubleshooting
• The cover provides protection from electrical shock hazards
• UL-listed and CE-marked
• Front of panel access

Main characteristics:

• P991 test module with provision for 14 circuits (cassettes)
• 6 different cassette options are available
• Test access is gained using P992 (multi-finger) and P993 (single-finger) test plugs
• All test plugs keyed to avoid inverted insertion, or insertion in an incorrect cassette type

Overall differentiation factors

• Testing is simplified and quickly performed
• Single-finger test plug converts measured current to a safe voltage for measurement to avoid a dangerous open-circuit
• Test wiring is prepared in advance on the P992 plug, prior to insertion - safer than step-by-step link-based test switches
• CT short-circuiting is performed safely within the block, rather than at the test plug, to minimise the chance of human error