Protection Application Handbook (англ. яз.)

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PROTECTION AND CONTROL EQUIPMENT

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failure trip simple can be arranged to trip the busbar, without need

of extra auxiliary contact on the disconnectors.

Figure 11. A trip busbar arrangement, for busbar protection tripping, gives a

simple solution and allows the CBF trip to be connected without extra auxil-

iary circuits on the disconnectors.

Lock out tripping.

Lock-out of circuit breaker closing should be initiated from protec-

tion relays covering faults of permanent type. Lock-out relays are

reset manually, when the fault has been repaired. The best solu-

tion is to open the close circuit only. A permanent signal in the trip

circuit only isn’t good as the breaker then can be unnecessary ini-

tiated even though instantaneously retripped. A continuous trip

will also mean problems for trip circuit supervision and special

care need to be taken for this.

It should also be remembered that a Breaker trip coil cannot ac-

cept more than a short trip pulse. Long pulses will destroy the trip

coils and this can happen e. g. when a Breaker has not stored en-

ergy in the operating device and the trip relay is initiated, mostly

then during testing.

Lock-out should thus preferable be performed with self reset trip

relays and latching relays opening the closing circuit only.

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Capacitive discharges.

Trip and important operation relays should be stable during the

capacitive discharges which can occur at an earth fault in the DC

system. The problem is shown in Figure 12. Special types of re-

lays with a stabilization against this discharge are available.

Figure 12. An earth fault in the battery system, will give capacitive discharg-

es, which can operate trip relays. Secured trip relays should be used when

the circuit is simply available e.g. in terminals.

SIGNALLING

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4. SIGNALLING

4.1 FAULT SIGNALLING

At a fault in the primary network it’s of importance that the oper-

ating personal receives information about fault type, whether the

fault is persistent or transient, what phases are involved and the

fault location so that correct actions can be taken.

At a fault in a the protection and control equipment it’s of great im-

portance that the operating personal receives information about

the disturbances so that corrective actions can be taken.

These faults don’t normally mean disturbance for the system ser-

vice but need to be repaired within a short time.

An alarm for a fault in the battery system like a lost battery charg-

ing need to be ﬁxed within 4-10 hours depending on the batteries

capacity so that the station is not left without protection and con-

trol possibilities. A fault in the primary system would then cause

unnecessary large consequence, with damaged equipment and

disconnection of far to big parts of the network as a result.

Several different equipment types are used to give information

about primary and control equipment faults. Among them you’ll

ﬁnd:

- Annunciator system

- Event recorder

- Disturbance recorder

- SCADA

One important part in order to achieve a high reliability and in or-

der to follow up disturbances in the primary system and the be-

havior of the protection system is the post fault analysis (see

Protection - General).

SIGNALLING

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4.2 ANNUNCIATOR SYSTEM

The annunciator system will give the operating personal quick in-

formation about a fault. At activation of an alarm point an audible

alarm is initiated. This alarm is locally switched off when the sta-

tion is remotely controlled.

All faults are to be alarmed but grouping in suitable groups is

done to save cost and to simplify for the operator as too much in-

formation will only be confusing when a quick decision have to be

taken.

4.3 EVENT RECORDER

The event recorders gives digital, time tagged, information about

all disturbances in the control system, as well as in the primary

system.

The sequence of events such as starting of measuring zones and

phase selection etc., can be followed with a resolution of some

ms which simpliﬁes the follow up on a disturbance. This follow up

is performed later by experts at protection and control systems.

Information at the event recorder is just to a low extent used by

the operators.

4.4 DISTURBANCE RECORDER

The disturbance recorder gives information about the analogue

signals during a primary fault. A few digital event are also con-

nected to get a time reference and a possibility to compare the

event recorder and disturbance recorders information.

The disturbance recorder starts when any protection relay starts

or trips. A pre-fault memory is included. The recording will there-

by include information from just before the fault (0.1-0.5 seconds)

to up to after the fault has been cleared.

Today print-outs is on regular paper but there is also a possibility

to send the information in series form to a computer, as software

support today is available to most types of recorders.

INTERLOCKING

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4.5 REMOTE SIGNALLING.

Most stations in the world, are today remotely controlled, or pre-

pared for remote control.

Locally available signals must be transmitted with high reliability

to the dispatch center and to the operators. This concerns signals

for faults in the primary system, as well as faults secondary in the

control system.

5. INTERLOCKING

The interlocking system will prevent human mistakes which can

lead to severe damages of equipment and/or injuries of persons.

With the development of today control system and the increasing

integration of circuits it is of greatest importance to always keep

the independence requirement between the operation circuits

and the interlocking circuits in mind. An equipment fault must not,

at the same time, cause an operation of a disconnector and an

enabling signal.

Independency does not necessary mean independent hardware

but the design of the circuit to achieve a highest possible reliabil-

ity is important.

6. DOCUMENTATION

A big amount of documentation is necessary for each station in

order to enable service, maintenance, fault ﬁnding, purchasing of

spare parts and extensions of the station. The documentation is

the output of a process starting at contract signing and ending

with the Final acceptance.

The cost of design and documentation is about 20-30% of the to-

tal cost of the control system.

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Documents for different categories

The documents produced are for varying categories of personal.

Erection, commissioning, maintenance and engineering depart-

ments, have all different requirements and uses different docu-

mentation in their work.

Documents groups

The documentation can be separated in three different parts:

- Operation and Maintenance manuals, gives information about operation

and maintenance of the station. General documents like Single-line di-

agrams, Block diagrams and User’s manuals for products, are included

here.

- Electrical design contains Circuit diagram, apparatus list and intercon-

nection tables etc., and gives detailed information to commissioning and

maintenance personal.

- Erection manuals includes information for mechanical construction such

as mounting information for panels and apparatus, mechanical draw-

ings etc. The erection manuals are used by the erection personal.

It is of utmost importance that the documentation is kept updated

and that old v

ersions are thrown away. An up-to-date set shall be

stored at the substation.

7. CONCLUSION

When a control system is designed it is important to see to the

goal with the substation and to check that the purpose with the

document produced is clear.

A reliable plant, with a high availability, shall be simple to operate

and maintain. Simple solutions are always preferred as mistakes

and misunderstandings during the different stages of the project

are prevented.

The documentation system has a key role as carrier of informa-

tion between different departments during the different stages of

the project. A well structured organization where responsibilities

are known by all people is necessary to achieve a high quality

and reliable plant with high availability.

TERMINAL NUMBERING SYSTEM

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8. TERMINAL NUMBERING SYSTEM

8.1 RELAY PANEL, MAIN 1 PROTECTION

Function Type Terminal group

Current circuit

Core 1 I1 X11: 11-14

Core 2 I2 (other CT:s 21-24

Core 3 I3 are called 31-34

Core 4 I4 X111 etc.) 41-44

Voltage circuit

Distr 1 U1 X12: 11-19

Distr 2 U2 (other VT’s 21-29

Distr 3 U3 are called 31-39

Distr 4 U4 X112 etc. 41-49

Open delta 51-59

Auxiliary voltage

protection relays

DC distr R2+/- X13: 1-16

PLC sign X17: 1-

Sub 1-Sub 2 Interface X18: 1-

Trip outputs X19: 1-

(incl CB fail, intertrip etc.)

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8.2 RELAY PANEL, MAIN 2 PROTECTION

Function Type Terminal group

Current circuit

Core 1 I1 X21: 11-14

Core 2 I2 (other CT:s 21-24

Core 3 I3 are called 31-34

Core 4 I4 X121 etc.) 41-44

Voltage circuit

Distr 1 U1 X22: 11-19

Distr 2 U2 21-29

Distr 3 U3 31-39

Distr 4 U4 41-49

Open delta 51-59

Auxiliary voltage

protection relays

DC distr R2+/- X23: 1-16

PLC sign X27: 1-

Sub 1-Sub 2 Interface X28: 1-

Trip outputs X29: 1-

(incl CB fail, intertrip etc.)

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8.3 OTHER CIRCUITS

Control circuits

DC distr X31: 1-10

Other circuits 21-

Annunciator circuits

DC distr X41: 1-10

Other circuits 21-

SCADA circuits

DC distr X51: 1-10

Other circuits 21-

Event recorder circuits

DC distr X61: 1-10

Other circuits 21-

Fault Recorder circuits

DC distr X71: 1-10

Other circuits 21-

DC Supply Main 1 (feeding MCB/fuse)

DC distr X91: 1-4

DC Supply Main 2 (feeding MCB/fuse)

DC distr X92: 1-4

AC Supply for Heaters Lighting etc.

AC distr X93: 1-10

Other circuits 21-

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