The LTB is a test block with extended rear terminals that allows for easy and safe disconnection of IEDs (protective relays, fault recorders, revenue meters, etc.) from the system side of the power grid. The LTB typically works in conjunction with the LTP test plug, which features an integrated leverage mechanism to assist with its insertion into the LTB.
The sophisticated mechanical design of the LTP ensures a seamless plug-in process for the test plug. This enables a quick disconnection of a large number of poles with just a few simple movements.
Closed circuit
An LTB test block consists of either 7 or 14 modular units, known as poles. Each pole is designated for a specific circuit: current, voltage, signal, or trip. These circuits are interconnected within the block using two silver-plated copper contacts. The contacts are securely pressed together by two pressure springs, ensuring a highly conductive electrical connection. This establishes an electrical link between the device side (B) and the system side (A).
Open Circuit
During testing, the corresponding LTP test plug is inserted into the test block using the leverage mechanism. This action effectively isolates the device and system sides of the test block from each other. The test plug is equipped with internal shorting bridges specifically designed for the current circuits. Upon removal of the test plug from the test block, the internal springs exert force on the contacts, causing them to reconnect and restore the circuits to their default closed position.
Signal Injection
The test plug features banana jacks on top, which enable the connection of a test set to the device side of the test block, facilitating signal injection for testing purposes.
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