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Test Interfaces for Power Systems



SAX is a surface mount terminal / test block combination for interfacing substation devices (protection relays, fault recorders, revenue meters, . . . ) to the voltage and current transformers and to other equipment on the system side of a power grid.

PAX is a test plug keyed to a particular configuration of SAX blocks. Once inserted into the corresponding SAX block, the PAX plug isolates the substation devices from the system side equipment while at the same time allowing connection of test equipment for secondary injection tests.

Key Features

  • Reducing Panel Space and Wiring Time Needs
    SAX combines the functions of two devices: a terminal block and a test block. This means that less panel space and less wiring is required. SAX can be placed in areas where normal test switches cannot be installed – easily mounted on a DIN rail or via screws
  • Finger-safe
    The front of the SAX terminal / test block has no exposed metallic parts, greatly increasing safety during testing.
  • Patented Keyed Test Plugs
    Test plugs are keyed to the corresponding test block, preventing mistakes and errors during testing. Current circuits are keyed different than other types of circuits, allowing the use of individual test probes while maintaining the safety benefits.
  • Built-in Time Sequencing
    When a test plug is inserted into a SAX test block, contacts are opened in a pre-defined sequence. This is done to prevent false trips from activating the breaker, greatly simplifying the task of testing. The intelligence is built into the plug: different length fingers create the sequence and fixed current shorting bars provide safe and reliable make-before-break current shorting. When the PAX test plug is removed from the block, contacts are closed in the reverse order, with the trip contacts being the last to close.
  • Less than 2 mΩ internal resistance
    Thanks to the patented construction, SAX / PAX test blocks have an extremely low internal resistance. This decreases the burden placed on instrumentation transformers and also reduces heat dissipation inside cabinets and panels.
  • Many sizes and configurations
    The right SAX for you either already exists or can easily be created. The 4600 series includes popular models with 7, 10, 14 and 20 poles. Custom configurations have 4 to 20 poles and can be built with any combination of currents, voltages or trip signals, as well as custom labeling.

Principle of Operation

Closed circuit
A SAX terminal / test block contains modular units (or “poles”) each allocated to a current, voltage, or signal / trip circuit. Each circuit is connected through the block via two silver-coated 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 PAX test plug or test probe is inserted into the SAX. In this position, the device and system sides of the terminal / 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 in the test plug allow the connection of a test set to the device side of the terminal / test block and the associated signal injection. Access to the system side is also provided.


Cases for PAX Test Plugs
Rugged case for PAX Test Plugs with handle or Test Probes.
Individual Test Probes
These test probes will fit all SAX 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 SAX Test Block). Current probes include 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.
SAX 19´´ Rack Plates
SecuControl offers metal plates for installation of SAX test blocks in 19” racks that come painted in various colors and with various cutouts for SAX 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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