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ElectricalDiagrams

FunctionalDiagrams

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AGENDA

GENERAL SINGLE WIRE DIAGRAMS FUNCTIONAL DIAGRAMS

Introduction AC functional diagrams Control and drive functional diagrams Practical criteria to design diagrams

WIRING DIAGRAMS

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Introduction This type of diagrams is called “functional” because they represent

the auxiliary elements of a device or set of devices linked to perform a given function. Hence, in these diagrams, the appearance of the switchgear is

not important, but its “function” inside the set of devices that constitute the transmission substation.

Apparatus such as disconnectors, circuit breakers and transformers with on-load tap changer, include driving devices, generally fed by DC. However, to operate a drive, there must be supervision means

to obtain an indication about how the devices respond to a given order. This means, every drive is associated to an indication device, and this set constitutes a CONTROL group.

This CONTROL group can be digital type, in which a signal exist or not, indicating two possible conditions of a given device (e. g.: 52 circuit breaker OPENED or CLOSED).

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Introduction It can also be analogical, in which the signal takes different values

depending on the condition of the controlled power system (e. g.: ammeter with scale 0-500 A, in which the current circulating through the supervised position can take any value between the extremes values of the scale).

Hence, for every position, a set of diagrams is elaborated, which relative order obeys almost exclusively to the functionality criterion, without considering its physical location inside the substation.

This greatly simplifies the diagrams design and its interpretation, since their purpose is to inform about how and under which conditions a device or set of devices will operate.

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Introduction For the study of any electric diagram, certain initial conditions shall

be given, which are, in principle, arbitrary and imposed by the observer.

To unify the criteria of elaboration and interpretation of the electric diagrams, some conditions of representation are adopted universally, which are the following: The circuits are represented without voltage and with the circuit

breakers opened. Therefore, there is not current circulation. All electric systems are passive.

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Introduction All the associated mechanical systems have null kinetics

energy and/or minimal potential energy. Hence: There is no fluids circulation in pipes. The liquids deposits are at minimum level. The gases deposits have no pressure. The thermal devices are at minimum temperature. There is no light incidence in the devices that operate under that

principle (photocells, optical couplers, etc.).

Any diagram elaborated according to a criteria different that those exposed above, should include a written indication of the criteria determined by the designer so the diagram can be correctly interpreted.

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AGENDA

GENERAL SINGLE WIRE DIAGRAMS FUNCTIONAL DIAGRAMS

Introduction AC functional diagrams Control and drive functional diagrams Practical criteria to design diagrams

WIRING DIAGRAMS

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AC Functional diagrams Show the relationship between the power system and the control

circuits in a more explicit fashion that the single-wire diagram. Part of this are the instrument transformers (current transformers

and voltage transformers) as a function of their characteristic values and the purpose of their secondary windings. This purpose can be divided in two basic functions:

Measurement: They provide measures of voltage and/or current to the measuring

devices, thus the operation personnel can know, at any time, the parameters of operation of the power system controlled from the substation.

Protection: They provide measures of voltage and/or current to the protection

relays, thus these relays can detect an abnormal situation and start an automatic sequence of operation to correct or eliminate the abnormality.

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AC Functional diagrams. Voltage measurement

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AC Functional diagrams. Voltage measurement In the diagram Y105.102, which continues from the former one, the devices that feed the busbar voltage circuits are shown: voltmeters V-B1 and V-B2; the ERAS (equipment for automatic reposition of service, by its acronym in Spanish); the measurement converters CMV-B1 and CMV-B2 to send telemetering to the remote control; and the undervoltage relays 27-B1/OSC and 27-B2/OSC.

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AC Functional diagrams. Current measurement

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AC Functional diagrams. Current measurement The diagram shows the current circuit of the COUPLING position. The power circuit comprises the circuit breaker 52-5 and the

disconnectors 89-5-1 and 89-5-2.

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AC Functional diagrams. Current measurement

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AC Functional diagrams. Current measurement Three groups of current transformers are shown, and one of them

have its secondary windings short-circuited, since it is out of service.

The group located on the side of busbars 1 provides the currents for the protection relays 51 and 51N.

The one located on the side of busbars 2 provides the currents for power and current measurement (power converter CMW-5 and ammeter A-5).

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AC Functional diagrams. Transformer bay

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AC Functional diagrams. Transformer bay The diagram shows the three-wire diagram of currents. A group of two current transformers is used for current

measurement. The group comprised by three current transformers is used for

protection, which is provided by two overcurrent relays (51) and the differential protective relay (87).

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AC Functional diagrams. Transformer bay

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AC Functional diagrams. Transformer bay This transformer has three windings:

Primary winding at 132 Kv Secondary winding at 66 kV Third winding at 11 kV

The connection groups are: Between primary and secondary windings: Yy0 Between primary and third windings: Yd11

The power that can be provided by the three windings in steady state is 30 MVA.

The diagram presents two current transformers located in the neutrals of the T-2 that provide polarizing currents for the directional overcurrent-to-ground relays (67N), which operate as a background line protection.

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AC Functional diagrams. Feeder bay

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AC Functional diagrams. Feeder bay Downstream the circuit breaker (the farther side from the busbars) it

is located a group of two current transformers for power and current measurement, as in the former cases.

Another group of three current transformers, also downstream the circuit breaker 52-8, feeds the currents to the OSCILLOSCOPE OSC-1, through some adapting auxiliary current transformers: TAC-1 and TAC-2, this last one in residual connection to provide the image of the fault-to-ground currents.

Other group of three current transformers, located upstream the circuit breaker 52-8, provides the currents for the protection relays: a set of three distance relays (21) type GCX51A, as the main protection and a directional overcurrent-to-ground relay (67N) type TCC511B, connected in residual connection (diagram Y105.402).

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AC Functional diagrams. Feeder bay

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AC Functional diagrams. Feeder bay The placement of the disconnectors is similar to that of the

transformer T-2, including the earthing switch 89-8-6 (diagrams Y105.401, 402, 403).

The diagram shows a capacitive voltage transformer with two secondary windings; solely one of them is used to provide voltage measuring local and remote to start the ERAS.

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AC Functional diagrams. Feeder bay

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AC Functional diagrams. Feeder bay In the diagram, it can be observed that the busbar voltages, supply

reference voltages to the distance relays and polarizing voltage to the relay 67N (besides the polarizing current indicated).

Those voltages also feed the power converter CMP-8 and the oscilloscope OSC-1.

Please observe that, by means of contacts of repeating relays of the busbars disconnectors (89-8-1X and 89-8-2X), solely voltages from the busbars connected to the line L-8 feed the instruments and relays.