Product Overview

The ABB PR111/P LSI SACE Emax Electronic Trip Unit is an electronic protection release used in ABB SACE Emax low-voltage air circuit breakers. It monitors current flowing through the circuit breaker and evaluates overload and short-circuit conditions to determine when the breaker must trip.

The PR111/P belongs to ABB’s self-powered electronic protection release family. It obtains its operating energy from the current transformers installed in the circuit breaker, eliminating the need for a separate auxiliary power supply for its basic protection functions.

The LSI configuration combines three protection functions: Long-time overload protection (L), Short-time short-circuit protection (S), and Instantaneous short-circuit protection (I). These functions allow the circuit breaker to respond to different levels of abnormal current according to their respective trip characteristics.

In industrial power distribution systems, electrical loads such as motors, transformers, production machinery, and distribution feeders can experience overloads or short circuits. Without appropriate protection, excessive current can damage cables, electrical equipment, and connected machinery.

The PR111/P LSI monitors the current measured by the circuit breaker’s current transformers. When the measured current exceeds the configured protection thresholds, the electronic release evaluates the corresponding protection condition and initiates a trip command.

For example, in a manufacturing facility, a motor feeder may experience an overload caused by excessive mechanical loading. The long-time protection function allows the circuit to tolerate temporary current increases while responding to sustained overload conditions. If a short circuit occurs, the short-time or instantaneous protection function can initiate circuit interruption according to the configured settings.

The PR111/P uses digital microprocessor technology and DIP switches for setting protection parameters. Its front panel also includes LED indicators for protection alarms, allowing maintenance personnel to identify certain abnormal operating conditions.

Another important feature is its backup protection function. If the first opening command does not successfully operate the circuit breaker’s opening mechanism, the release can repeatedly issue TRIP commands until the breaker opens or the current disappears.

The PR111/P is intended for integration with compatible three-pole, three-pole with external neutral, and four-pole Emax circuit breakers. The exact breaker frame, rated current transformer configuration, and release version must be checked before selecting a replacement.

For industrial electrical maintenance teams, the ABB PR111/P LSI provides electronic overcurrent protection for compatible SACE Emax circuit breakers, supporting coordinated protection of low-voltage power distribution equipment.

Technical Specifications

Product Features

• LSI Protection Configuration: Combines long-time, short-time, and instantaneous overcurrent protection.
• Self-Powered Operation: Obtains operating energy from the circuit breaker’s current transformers.
• Microprocessor-Based Protection: Processes current measurements and evaluates protection conditions digitally.
• Adjustable Protection Settings: Uses front-panel DIP switches to configure protection parameters.
• Backup Protection: Repeats TRIP commands if the initial opening command does not successfully interrupt the circuit.
• Watchdog Function: Monitors the protection release’s operating condition.
• Test Function: Supports testing of the protection release.
• LED Alarm Indication: Provides visual indication for L and S protection alarms.
• Multiple Breaker Configurations: Supports compatible three-pole and four-pole circuit breaker arrangements.
• Neutral Current Processing: Supports different neutral-current processing relationships relative to the phase currents.

Working Principle

The ABB PR111/P LSI operates by measuring current through the current transformers installed in the SACE Emax circuit breaker. Its microprocessor evaluates the measured current against the configured protection parameters and determines whether a trip command is required.

The protection process consists of three principal functions.

Long-Time Overload Protection (L)

The L function protects electrical circuits against sustained overload conditions.

When current exceeds the configured long-time pickup threshold, the electronic release begins evaluating the overload condition according to its inverse-time characteristic.

This allows temporary current increases without immediately opening the circuit breaker. If the overload continues, the release initiates a trip command after the corresponding delay.

In applications involving electric motors and industrial distribution feeders, this function helps protect conductors and connected electrical equipment against prolonged excessive current.

Short-Time Short-Circuit Protection (S)

The S function responds to short-circuit currents that exceed the configured short-time threshold.

Unlike instantaneous protection, short-time protection includes an adjustable delay. This allows coordination between upstream and downstream circuit breakers.

For example, when a fault occurs in a downstream distribution branch, the downstream breaker can be given the opportunity to interrupt the fault before the upstream Emax breaker trips.

The PR111/P supports selectable short-time protection characteristics, including constant-time and inverse-time behavior, according to the applicable settings.

Instantaneous Short-Circuit Protection (I)

The I function responds to high short-circuit currents without an intentional time delay.

When the measured current reaches the configured instantaneous threshold, the electronic release issues a trip command to interrupt the circuit.

This function is particularly important for severe short-circuit conditions where rapid disconnection is required to limit electrical and thermal stress.

Current Measurement and Self-Powered Operation

The current transformers installed in the circuit breaker provide both the current measurement signals and the energy required for the electronic release.

The PR111/P uses these signals to calculate the current flowing through the circuit breaker and evaluate the protection conditions.

An important selection consideration is that the reference current for the PR111/P is the rated current of the current transformers (In), rather than the uninterrupted rated current of the circuit breaker itself (Iu).

Trip Command and Backup Protection

When a protection condition requires interruption, the PR111/P sends a command to the circuit breaker’s opening solenoid (SA).

The solenoid operates the mechanical opening mechanism, separating the breaker contacts and interrupting the current.

If the first opening command does not successfully open the circuit breaker, the backup protection function repeatedly issues TRIP commands until the breaker opens or the current disappears.

Role in the ABB SACE Emax Protection Architecture

The PR111/P LSI serves as the electronic protection component inside the ABB SACE Emax air circuit breaker. It monitors electrical current and controls the trip operation through the circuit breaker’s opening mechanism.

A simplified protection arrangement follows this structure:

Power Supply → Current Transformers → PR111/P LSI → Opening Solenoid → Circuit Breaker Contacts

In an industrial distribution panel, the PR111/P receives current information from the current transformers mounted in the Emax breaker. It evaluates the current against the selected protection settings and initiates the opening mechanism when a fault condition is detected.

Its LSI functions also allow protection coordination between circuit breakers at different distribution levels.

Industrial Applications

Installation and Maintenance

1. Verify the Trip Unit Model: Confirm that the replacement is ABB PR111/P with the LSI protection configuration.
2. Check Circuit Breaker Compatibility: Verify the Emax breaker model, pole configuration, and rated current transformer arrangement.
3. Confirm Current Transformer Rating: Check the In rating of the installed current transformers because the PR111/P uses this value as its protection reference.
4. Record Existing Settings: Document the L, S, and I protection settings before removing the existing release.
5. Isolate the Circuit Breaker: Disconnect the electrical supply and follow the required lockout and safety procedures before accessing the trip unit.
6. Inspect the Release Assembly: Examine the electronic release, mounting points, connectors, and associated wiring for visible damage.
7. Check the Opening Solenoid: Inspect the SA opening mechanism and associated connections according to the breaker maintenance procedure.
8. Install the Replacement Unit: Follow the ABB installation instructions to position and secure the PR111/P correctly.
9. Configure Protection Parameters: Set the L, S, and I protection values according to the approved electrical protection coordination study.
10. Verify Neutral Configuration: For breakers with an external neutral or four-pole arrangement, confirm that the neutral-current processing settings are appropriate.
11. Perform Protection Testing: Use the prescribed ABB test procedure to verify the release functions and circuit breaker trip operation.
12. Document Commissioning Results: Record the installed release identification, current transformer rating, protection settings, and test results before returning the breaker to service.

Compatible System Components

Recommended Related Models

Key Advantages

• Combines three essential overcurrent protection functions in one electronic release.
• Uses current transformers for measurement and self-powered operation.
• Supports adjustable long-time and short-time protection settings.
• Provides instantaneous short-circuit protection.
• Includes backup trip functionality.
• Offers watchdog and test functions for protection system maintenance.
• Supports multiple SACE Emax pole configurations.
• Uses DIP switches for protection parameter configuration.

Technical FAQs

What does LSI mean on the ABB PR111/P trip unit?

LSI refers to three protection functions: L for long-time overload protection, S for short-time short-circuit protection, and I for instantaneous short-circuit protection. This configuration provides different response characteristics for sustained overloads and short-circuit faults.

Does the PR111/P require an external auxiliary power supply?

The PR111/P is a self-powered electronic protection release. It obtains its operating energy from the current transformers installed in the circuit breaker. A separate auxiliary power supply is not required for its basic protection operation.

Can the PR111/P LSI be installed in a four-pole SACE Emax breaker?

Yes. ABB documentation identifies compatibility with three-pole, three-pole with external neutral, and four-pole circuit breaker configurations. The exact breaker model and current transformer arrangement must still be checked before installation.

What is the difference between PR111/P LSI and PR111/P LSIG?

Both releases provide long-time, short-time, and instantaneous protection. The LSIG version additionally includes earth-fault protection with adjustable delay. The appropriate version depends on the required electrical protection scheme.