Intelligent Systems in Power System

Information for:

Security Assessment

Fault Analysis

Power System Protection

Figure 8.

Take a look at figure 8 and think about it for a second.

What can you tell from figure 8?
There is a fault between Vignole and Baggio. It is possible that a relay or breaker at Castelnuov is malfunctioning or something is wrong with the subsation.

Is there any malfunction involved? Why?
Yes. A breaker at Castelnov should open.

Can you find the de-energized zone by observing the system? What’re the components of the de-energized zone?
Yes. The components are:

Line between Vignole-Castelnuov

Line between Castelnuov-Baggio

Castelnuov substation

Figure 9. Hypothesis for the third case

Now look at the SER report data below:

Index	Date	Time	Time (msec)	Substation Name	Volt (kV)	Line Name	Line No.	Status	Component

Figure 10.

Explain what really happen in the SER data by using a sentence or two describing each protection and recovery action (combine the same action, for example 1-3 see the fault and start the distance relay).

(1-11) All of these substation see the fault. Those substations that see the fault in first zone will start the protection system.

(12) The relay at Vignole B is tripped.

(13) Castelnuov received a signal to block the reclosure.

(14) Breakers at Vignole is opened.

(15-19) The relays decided the fault was permanent so they blocked the reclosure.

(20-21) The relay at Castelnuov is malfunctioning that's why it started the 2nd transition.

(22)The relay at Baggio sent a tripping signal to the breaker as a backup relay.

(23-25)These substations see the fault in the 2nd zone.

(26-27) Ph A,B, and C breakers at Baggio were opened.

(29) Reclosing at Baggio has cleared

(30) Automatic reclosure at Vignole B

(31) Breaker at Vignole was closed

(32-37)These substations see the fault again and start the relay.

(38) The relay atVignole B is tripped for the second time.

(39-41) The second relay trip at Vignole B causes the three phase breakers to open.

How long does it take for the relay to trip?
100 milli seconds

How long does it take for the breaker to open after the relay trip?
55 milli seconds

Can you think of any reason why the substation in the SER data above try to block the reclosure?
Because it is a permanent fault.

What kind of information is necessary to decide that the second hypothesis is the correct scenario?
This is an open ended question. One of many possible answers is to state that the SER report shows the real scenario.

Additional questions to consider:

Given any of the hypotheses:

Draw the one line diagram that supports the hypothesis.
Create the SER data that support each of the hypotheses.

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