Lockouts and auto-reclosures are apprentices of power systems protection that have long served to regulate power supply and safeguard important components from probable catastrophes. But are we taking them seriously enough? In implementing the lockout features, apart from their placements in control circuitry, operating principles, construction, and functionalities almost the same over decades, while their counterparts have seen massive overhauls.
This article will focus on the practical applications of lockout relays on mainstream switchgear and protection. The primary goal is to discuss the transition from the current mode of application to possible upgrades and adaptations in modern digital power substation protection.
The terminologies lockout relay, master trip relay, and 86-relay are used interchangeably in this article.
Protection relays are undoubtedly the soul of substation protection and require multiple auxiliary relays to support them for the overall functionality of protection, control, and monitoring. Master trip relay or lockout relay, also known by ANSI code 86, holds a significant position as an intermediator between the protection relay and control points, even though it is not self-equipped with .
The master trip relay can operate as a hub of multiple protection relays trip commands and drive multiple subsequent contacts. This makes the relay a protagonist to execute simultaneous commands like .
In the absence of a master trip relay, imagine connecting individual trip circuits of each protection relay to circuit breaker trip coils. Along with the obvious extra cost incurred, this would be a mess for operation and troubleshooting. The concept of lockout relay as an intermediator of protection is illustrated in Figure 1.
In modern day protection IED activates the lockout relay to perform the trip command of associated breakers. Likewise, the command for a closing coil of breaker only receives the close signal upon confirmation from the lockout relay.
The sequence of operation for medium voltage switchgear with numerical protection relay to execute closing command is illustrated in Figure 2
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Lockouts and auto-reclosures are apprentices of power systems protection that have long served to regulate power supply and safeguard important components from probable catastrophes. But are we taking them seriously enough? In implementing the lockout features, apart from their placements in control circuitry, operating principles, construction, and functionalities almost the same over decades, while their counterparts have seen massive overhauls.
This article will focus on the practical applications of lockout relays on mainstream switchgear and protection. The primary goal is to discuss the transition from the current mode of application to possible upgrades and adaptations in modern digital power substation protection.
The terminologies lockout relay, master trip relay, and 86-relay are used interchangeably in this article.
Protection relays are undoubtedly the soul of substation protection and require multiple auxiliary relays to support them for the overall functionality of protection, control, and monitoring. Master trip relay or lockout relay, also known by ANSI code 86, holds a significant position as an intermediator between the protection relay and control points, even though it is not self-equipped with .
The master trip relay can operate as a hub of multiple protection relays trip commands and drive multiple subsequent contacts. This makes the relay a protagonist to execute simultaneous commands like .
In the absence of a master trip relay, imagine connecting individual trip circuits of each protection relay to circuit breaker trip coils. Along with the obvious extra cost incurred, this would be a mess for operation and troubleshooting. The concept of lockout relay as an intermediator of protection is illustrated in Figure 1.
In modern day protection IED activates the lockout relay to perform the trip command of associated breakers. Likewise, the command for a closing coil of breaker only receives the close signal upon confirmation from the lockout relay.
The sequence of operation for medium voltage switchgear with numerical protection relay to execute closing command is illustrated in Figure 2
This technical article/guide requires a Premium Membership. You can choose an annual based Plus, Pro, or Enterprise membership plan. Subscribe and enjoy studying specialized technical articles, online video courses, electrical engineering guides, and papers. With EEP's premium membership, you get additional essence that enhances your knowledge and experience in .
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