ANSI Numbers! 52 means breaker. 52A, 52B indicate breaker status; However, few SEL relays have some funny numbers never seen before. 52AA, 52AB, Hmm..

ANSI Relays Numbers! 52 means breaker. 52A, 52B indicate breaker status; However, few SEL relays have some funny numbers never seen before. 52AA, 52AB, 52AC.?Hmm ..

Quiz #1: See the picture below for the quiz.?

The background behind this quiz:?

Some engineers were working on documenting relays in their facility; They were reviewing their company's internal specifications and noticed the following 52AA, 52AB, and 52AC.

They thought someone had made a mistake because 52AA, 52AB, and 52AC are not on electrical standards codes. So, they thought the document should be corrected and removed the second letters on each symbol. I smiled when I found out. I decided I may explain this concept by formulating a quiz. Let's explain it.

ANSI (American National Standards Institute) established some numeral notations for protective devices. 52 means AC breaker. When you look at drawings or schematics and see the number 52, there is an AC breaker somewhere.

There is other ANSI number device, 52A and 52B. They both indicate breaker contact positions. 52A contact opens when the breaker (52) opens. 52A contact closes when 52 closes. On the other hand, 52B opens when 52 is closed, and 52B closes when 52 opens.

All relay and breaker manufacturers in north America follow that ANSI device logic. However, looking at the logic of SEL transmission protection relays, you will see 52AA, 52AB, and 52AC. I do not know if SEL brands are the only ones with those numbers in the transmission protection area.

Let's pick one of those relays with those codes: SEL 311L: Line current differential protection.

I took a screenshot of the manual, and you can see those codes in Figure 1 below.

Callout 1 in Figure 1 states 52AA circuit breaker pole A status. Assert to logical 1 when breaker pole A is closed.?

Callout 2 in Figure 1 states 52AB circuit breaker pole B status. Assert to logical 1 when breaker pole B is closed.?

Callout 3 in Figure 1 states 52AC circuit breaker pole C status. Assert to logical 1 when breaker pole C is closed.?

Unlike breakers in electrical distribution and generation, we want to be able to know the status of an individual pole. For example, if a tree falls into one phase of a transmission line, we want to know that only one phase had an issue and be able to try to reclose that breaker pole.

Those codes 52AA, 52AB, and 52AC allow us to establish a single pole reclosing.

Fun question:?

1-????now that SEL 311L has 52AA, 5AB, and 52AC, does 52A still exist? If yes, what is the relationship between 52A and 52AA, 52AB, and 52AC?

2-????Since 52B is an ANSI code. Do you think the SEL 311L also has 52BA, 52BB, and 52BC?

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