---

What is a Lockout Relay (LOR)?

When faults happen in power systems, safety devices protect equipment and people. The lockout relay 86 (LOR) is one of the most important safety devices. It is also called ANSI 86.

Think of the Lockout Relay 86 (LOR) as a safety lock on your electrical system. Its job is simple but vital. Once a circuit breaker opens due to a fault, the LOR keeps it locked in the “OFF” position.

No one can turn it back on—not even by accident. First, a trained electrician must check the system. Then, the problem must be fixed. Finally, the relay can be unlocked by hand.

This simple device prevents a very dangerous situation. As a result, power cannot be turned back on when a fault still exists.

What Does a Lockout Relay Do?

The LOR is also called the Master Trip Relay or 86 relay. It is a safety device. It keeps circuit breakers open after severe faults occur.

Standard relays simply send a trip command. However, the lockout relay 86 LOR adds extra safety. Moreover, it stops any closing attempts. This continues until a person takes action.

The LOR provides fail-safe protection. Therefore, circuits cannot be turned on again while faults still exist in the system.

The Problem It Solves

Imagine this. A fault triggers your relay. The relay sends a trip command to the circuit breaker. As a result, the breaker opens and stops the faulty section.

However, what happens next? Someone might send a close command to that breaker. This could happen before the fault has been fixed.

Without a lockout relay 86 (LOR), the breaker would close onto the fault. This could cause:

• Severe damage to the breaker itself
• The fault getting worse
• Risk of fire or explosion
• Danger to workers

Fortunately, the 86 relay stops this dangerous event.

How Does the Lockout Relay Work?

Basic Function

The LOR works using a latch and electrical coils. Once activated, the relay locks into place. Furthermore, it cannot be released without manual action.

Inside the Relay

The 86 relay uses two coils:

1. Trip Coil

The trip coil connects to the relay contact. This contact gets the trip command.

When energized, it latches the relay into the lockout position. At the same time, it opens the contacts in the closing circuit.

2. Reset Coil

A reset button energizes this coil. Only a trained technician can activate this coil. After the fault is cleared, it returns the relay to normal.

How It Works Step by Step

Here’s what happens when a fault occurs:

1. Fault Happens: First, a fault occurs in the power system
2. Relay Detects It: Next, the relay detects the problem
3. Trip Command Sent: Then, the relay closes its contact
4. Lockout Engages: Current flows through the 86 relay coil
5. Relay Locks: As a result, the relay locks into place
6. Closing Circuit Breaks: Meanwhile, the contact in the closing circuit opens
7. Breaker Trips: The breaker gets the trip signal and opens
8. Lockout Stays Active: Finally, the relay stays latched even after the trip signal ends

The breaker now cannot close. It stays locked until a technician resets the relay. First, the technician must confirm the fault is gone.

Where Are Lockout Relays Used?

In Substations

In substations, LORs provide protection for:

Transformer Faults: When faults occur inside transformers, the 86 relay stops power from turning back on. Otherwise, this could cause an explosion.

Bus Faults: When severe bus faults happen, a full check is needed before power is restored.

Breaker Failure: If a breaker fails, the LOR can trip backup breakers.

In Power Plants

Power plants use LORs for:

• Generator Protection: They protect against problems in rotating machines
• Multiple Breaker Control: They trip several breakers at once for single faults
• Equipment Safety: They keep expensive equipment off during faults

In Factories

Factories depend on LORs for:

• Protecting valuable equipment
• Managing protection across complex networks
• Meeting safety standards

How to Reset the Relay

Reset Methods

Resetting an LOR requires manual action by trained staff. This is a key safety feature. It ensures faults are checked before power is restored. The 86 relay offers two main reset methods:

Handle Reset

A physical lever is on the relay face. It gives clear confirmation of reset. Also, no electrical power is needed for reset.

Button Reset

This method allows remote reset through control circuits. It energizes the reset coil. Often, it includes monitoring capability.

Testing the Lockout Relay

Regular testing ensures the relay works when needed most. Here’s how to test it based on industry standards:

Before Testing

Before testing begins, do a visual check:

• First, verify all parts move freely
• Next, check for dirt or rust
• Then, ensure the reset works smoothly
• Finally, inspect contacts for damage

Testing Steps

Step 1: Setup

First, remove the relay from its case. Next, connect it to test equipment. Before applying voltage, verify all connections.

Step 2: Voltage Test

Slowly increase voltage to the coil. Then, record the voltage where the relay latches. Document the operation time. Finally, compare this to the specs.

Step 3: Drop-off Test

After the relay operates, slowly decrease voltage. Record the voltage where the relay releases. Also, note the return time.

Step 4: Ratio Check

Calculate the reset ratio using this formula:

Reset Ratio = (Drop-off Voltage / Pick-up Voltage) × 100%

A healthy relay shows a ratio between 90 and 95%. However, big differences mean there are problems.

Step 5: Coil Check

Measure the resistance of both coils. Then, compare results to the nameplate. When differences exceed 10%, investigate further.

Step 6: Reset Check

Test both reset methods. Ensure proper engagement and release. Also, verify the reset indication if present.

Step 7: Contact Check

Measure contact resistance. Check the continuity of all circuits. Also, test insulation between circuits. Finally, verify proper sequences.

How Often to Test

According to IEEE standards, LORs should get:

• Yearly visual check: Check for physical damage
• Every three years: Do complete electrical testing
• After each fault: Verify proper function before use

Wiring the Lockout Relay

Understanding the wiring is vital for proper setup. The wiring connects the relay into your control circuit. It intercepts both trip signals and closing commands.

Main Wiring Parts

A typical 86 relay wiring includes these key connections:

1. Trip Input

The coil connects to relay trip contacts. It receives 125V DC or 48V DC control power. Wire terminals are labeled as “TC” or “Trip Coil.” Furthermore, multiple relays can connect in parallel.

2. Trip Output

NC (Normally Closed) contacts interrupt the breaker closing circuit. These contacts open when the LOR operates. As a result, any closing command is stopped. They are usually rated for 125V DC.

3. Reset Circuit

A manual reset button connects to the reset coil. It requires a separate power source. Terminals are marked as “RC” or “Reset Coil.” Often, a contact is included to prevent accidental reset.

4. Alarm Contacts

Extra contacts provide status indication. They connect to alarm panels or computer systems. This helps operators know which relay operated. Typically, both NO and NC contacts are available.

Wiring Example

Here’s a simple circuit with an LOR:

• Relay Trip Contact → 86 Coil → Return to Negative
• Positive → Breaker Close Button → 86 NC Contact → Breaker Coil → Negative
• Positive → Manual Reset Button → 86 Reset Coil → Negative

In this setup:

When a fault occurs, the relay energizes the 86 coil. Then, the LOR latches. The NC contact opens, breaking the closing circuit. Therefore, the breaker cannot close until the reset button is pressed. After reset, the NC contact closes again and restores normal control.

Important Wiring Tips

When installing an LOR:

• Never bypass the lockout contacts—this defeats the safety purpose
• Use proper wire size—use 14 AWG minimum for control circuits
• Label all wires clearly—this aids troubleshooting
• Test the circuit—verify proper operation before energizing equipment
• Follow manufacturer diagrams—each relay model may differ
• Maintain isolation—keep trip and close circuits separate

Installation Tips

Panel Mounting

Most LORs mount on standard 35 mm DIN rails or directly to panels. Consider:

• Easy access for operators
• Clear visibility of indicators
• Protection from environment
• Adequate space for wiring

Benefits of Using Lockout Relays

Safety Benefits

Personnel safety is the main benefit. By preventing accidental re-energization, LORs protect:

• Maintenance technicians
• Operations staff
• The general public near facilities

Equipment Benefits

Expensive power equipment gains extra protection:

• Power transformers worth hundreds of thousands of dollars
• Circuit breakers with limited capability
• Generators and rotating machines
• Control and instrumentation systems

Reliability Benefits

Good lockout schemes improve overall system reliability by:

• Ensuring thorough fault investigation
• Preventing damage escalation
• Reducing unplanned outages
• Supporting proper fault analysis

Fixing Common Problems

Relay Won’t Operate

Possible causes:

• Low voltage to coil
• Mechanical binding
• Open circuit in wiring
• Damaged coil insulation

Relay Won’t Reset

Check these areas:

• Mechanical linkage problems
• Low reset coil voltage
• Stuck contacts or latch
• Reset circuit wiring problems

False Lockouts

If the relay operates without real faults:

• Check for wiring short circuits
• Investigate false relay operations
• Verify proper relay settings
• Review recent system changes

Summary

The Lockout Relay (ANSI 86) solves a key safety problem. It physically prevents a breaker from closing again after it trips due to a fault. Therefore, a person must check the system before power is restored.

This device is essential in power plants, substations, and factories. It prevents equipment damage, protects workers, and ensures safe system restoration.