ODES ANSI-Type Test Switches for Secondary Circuits

Re-engineering Safety in Relay Testing

In ANSI-based protection systems, commissioning teams must achieve two goals simultaneously: guarantee zero CT open-circuit risk and complete isolation, measurement, and verification within limited panel space.

A well-designed ANSI-type test switch and plug assembly transforms these complex tasks into a single, repeatable operation. The ODES TSBA Series Test Switch from ODES is purpose-built for this environment.

It incorporates a mechanical make-before-break interlock that automatically shorts CT circuits before isolation and uses a modular structure compatible with North American panel layouts and operating practices.

Mechanical Interlock Logic: Short Before Open

An open CT secondary can produce dangerously high voltages and equipment damage. The TSBA design eliminates this hazard through hardware-based sequencing:

• When the switch is opened, the CT secondary terminals are shorted first, and the current circuit is then interrupted.

• When the switch is closed, the current path is re-established before the shorting link is released.

This sequence is achieved entirely through mechanical coupling—no external shorting jumpers or manual intervention. Each insertion or withdrawal automatically follows the same safe order, regardless of operator experience.

Typical applications

• Periodic relay testing and calibration—safe isolation and measurement without transient CT open-circuit conditions.

• Commissioning or system energization—frequent switching with built-in CT protection.

ANSI-Standard Compatibility: Test Switch-A and Plug-A

The ODES TSBA corresponds to the ANSI Type A Test Switch and is paired with the FTA Series Test Plug-A. Available in 14-pole, 10-pole, and single-pole (FTA-S) versions, both are fully compatible with 4-mm DCC test leads widely used across North American utilities.

The FTA plug includes mechanical alignment and anti-reverse features, ensuring correct orientation every time. Each test point matches the numbered terminal on the switch, and the ergonomic handle design reduces fatigue during repetitive operations.

Recommended practice Before performing current measurements, connect the test instrument first, then insert the plug—confirming that the switch blades are in the open position before engagement. This procedure minimizes electrical and personnel risk.

Application examples

• Stepwise testing of protection and metering circuits—one plug serves multiple modules without rewiring.

• North American or export projects—directly compatible with regional tools and testing standards, reducing accessory cost and adaptation effort.

Engineering Benefits

• Built-in make-before-break protection eliminates CT open-circuit hazards.

• ANSI-standard interface ensures interchangeability and user familiarity.

• Modular construction simplifies integration into panel assemblies.

• Operator comfort through ergonomic plug design for frequent use.

• Consistent, auditable operation across all testing stages.

The TSBA Series ANSI-Type Test Switch combines internationally recognized form factors with intrinsic mechanical safety. Its make-before-break interlock automatically protects CT circuits, while the standardized FTA plug provides a unified interface for commissioning, calibration, and maintenance.

By embedding safety and consistency directly into the hardware, the TSBA Series allows every test operation to be carried out with precision and confidence.

Ensure your relay testing follows ANSI best practices—without additional wiring or manual shorting devices.

• Request detailed drawings and specifications for the TSBA and FTA Series.

• Consult with ODES engineers about integrating ANSI-type test switches into your protection panels.

• Make safety and repeatability a permanent feature of your commissioning process.

Contact: 📩 tonyzhang@odes.com.cn

Or visit: 🌐 https://www.odes-electric.com/

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