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Test Interfaces for Power Systems

Long Test Block


The LTB is a test block with extended rear terminals and allows easy and safe disconnection of IED's (protective relays, fault recorders, revenue meters, ...) from the system side of the power grid. The LTB typically works together with the LTP test plug which features an integrated leverage mechanism to aid with the insertion into the LTB.

The sophisticated mechanical functioning of the LTP contributes to an effortless plug-in process of the test plug. A large number of poles hence can be quickly disconnected with a few simple movements.

Key Features

  • Finger-safe
    There are no exposed metallic parts either on the LTB or the LTP, greatly increasing safety during testing.
  • Long back end
    Long back end of the LTB typically is flush with adjacent devices and makes cabling easier.
  • Guiding rail
    The LTP locks into the LTB for a secure fit.
  • Lever on test plug
    Leverage mechanism ensures smooth and even insertion of LTP Test Plug.
  • Ergonomic design
    The lever is made up of an ergonomic handle which can be turned effortlessly.
  • Choice of signaling color
    The plastic parts usually come in black, but the LTP is also optionally offered in orange as a signaling color.

Principle of Operation

Closed Circuit
An LTB test block contains either 7 or 14 modular units (or poles), each allocated to a current, voltage, signal or trip circuit. Each circuit is connected through the block via two silver-plated copper contacts, pressed securely together by two pressure springs to create a highly conductive electrical connection. In this situation, an electrical connection is established between the device side (B) and the system side (A).
Open Circuit
When testing, the corresponding LTP test plug is inserted into the test block via the leverage mechanism. In this position, the device and system sides of the test block are isolated from each other. The test plug includes internal shorting bridges for the current circuits. When the test plug is removed from the test block, the internal springs force the contacts back together, returning the circuits to their normally-closed position.
Signal Injection
Banana jacks on top of the test plug allow the connection of a test set to the device side of the test block and the associated signal injection.


Cases for LTP Test Plugs
Rugged case for LTP Test Plugs with handle or Test Probes.
Individual Test Probes
These test probes will fit all LTB Test Blocks, regardless of configuration. Keying in the probes prevents insertion into wrong circuits (ie, 2-pole current probes can only be inserted into a 2-pole current part of an LTB Test Block). Current probes include an internal shorting bridge.
Current Measurement Probe
This special test probe allows the connection of current measurement device or a shunt. The AWG 13 (2.5 mm) connection cable has a length of 118.11 inch (3 meters). The test probe are available with c-hook terminals or banana plugs at the tip of the cable.
LTB 19´´ Rack Plates
SecuControl offers metal plates for installation of LTB test blocks in 19” racks that come painted in various colors and with various cutouts for LTB test blocks, in standard heights of 2U or 3U.

Please consult our manual on the download section of this site for ordering information.



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