INTRODUCTION

• DTL a successor company of erstwhile Delhi Vidhut Board (D.V.B.) comes in to existence First July 2002, as a state transmission utility of the national capital of Delhi. After unbundling of D.V.B the distribution sector has been handed over to private companies while generation and transmission are still with government.

• VISION 2021- D.T.L. aiming to make Delhi a global metro politic and world class city. DTL has the responsibility playing its role in establishing upgrading, operating and maintain the E.H.V. (extra high voltage) network.

EXISTING AND PROPOSED SUBSTATIONS

Existing 400 kV substations• Bawana • Bamnauli Proposed 400 kV substations• Mundaka• East of loni (harsh vihar)

Proposed 220Kv substations

• Ridge valley• DIAL• AIIMS• Electric lane• Masjid Moth• Peragarhi• Wazirpur• Rohini

Existing 220 kV substations• Narela• Patparganj• Najafgarh• Mehrauli• Okhla• IP Extension• Gopalpur• Shalimar Bagh• Rohini• South of Wazirabad• Sarita vihar• Vasant kunj• Naraina• Gazipur• Pappankalan-1• Kanjhwala• Sabjimandi• Kashmere Gate• Geeta colony• Pappankalan-2• DSIDC bawana• Lodhi road• Park street

SWITCH YARD

Introduction to Switch Yard

Switchyard is a switching station which has the following credits:

• Main link between generating plant and Transmission system, which has a large influence on the security of the supply.

• Step-up and/or Step-down the voltage levels depending upon

the Network Node. • Switching ON/OFF Reactive Power Control devices, which

have effect on Quality of power.

SWITCHYARD EQUIPMENTS

Equipments commonly found in switchyard:

• Lightening arrestor• Current transformer• Voltage transformer• Power transformers / I.C.T.• Bus bar and clamp fittings• Support structure• Isolators• Circuit Breaker• Wave traps• Earthing switch

CLASSIFICATION OF SUBSTATION

The substation may be classified in numerous ways such as on the basis of

Nature of duties.• Step-Up or primary substation.• Step-Down or distribution substation.

Service rendered.• Transformer substation.• Switching substation.• Converting substation.

Operating voltage.• High voltage substation (11 kV-66kV) • Extra high voltage (132 kV-400 kV)• Ultra high voltage (above 400 kV)

Importance and design.• Indoor substation.• Outdoor substation.

TRANSFORMER

Introduction to Transformer

• A transformer is a static device that transfers electrical energy from one circuit to another without change in frequency through inductively coupled electrical conductors is known as transformer.

• By appropriate selection of the numbers of turns, a transformer thus allows an alternating voltage to be stepped up — by making NS more than NP — or stepped down, by making it less.

IDEAL POWER EQUATION• If the secondary coil is attached to a load that allows current to flow, electrical

power is transmitted from the primary circuit to the secondary circuit. Ideally, the transformer is perfectly efficient; all the incoming energy is transformed from the primary circuit to the magnetic field and into the secondary circuit. If this condition is met, the incoming electric power must equal the outgoing power.

• Pincoming = IPVP = Poutgoing = ISVS

The induced voltage (V) in a transformerV = 4.44 * N * B * A * f volts

– Where N = Number of winding turns B = Flux density value (Tesla)

• A = Core limb area (m2)• f = Frequency of applied voltage (cycles/sec)

DATA PLATE OF 100MVA T/F220/33KV

(STEP DOWN TRANSFORMER) MANUFACTURED BY- CROMPTON GREAVES LTD

INSTRUMENT TRANSFORMER

Introduction to Instrument Transformer

The main functions of instrument transformer are:– To provide insulation against the high voltage of power circuit and to protect

the apparatus and the operating person.– To supply protective relays with current and voltage of magnitude

proportional to those of the power circuit but sufficiently reduced in magnitude so that the relays can be made relatively small and inexpensive.

– Possibility of different types of secondary connections to obtain the required currents and voltages.

For the safety purpose the secondary of instrument transformer are grounded. It is mainly consisting of three types;• Current transformer (C.T)• Potential transformer (P.T)• Capacitive voltage transformer (C.V.T)

CURRENT TRANSFORMER

C.Ts are connected in an a.c power circuits to feed the current coils of indicating and metering instruments (ammeters, wattmeter, watt-hour meter) and protective relays.

Purpose:

To step-down the high magnitude of current to a safe value to incorporate Measuring and Protection logics.Current transformers are used for the instrumentation, protection or metering of power systems.

Ratio 800-400/1A - 1A - 1ABurden 30VA - -- - --Class of accuracy 0.2 - PS - PSKnee point volt. -- - 40V- 40V Max exciting current -- -30mA-30mAShort time current 31.5 KA for 3 secRated dynamic current 78.75 KA peakHighest system voltage 36 KVSystem voltage 33 KVRated continuous current 1.2 timesInsulation level 70 KV/170 KV (peak)Insulation class AInstallation ODType of cooling ONVolume of oil (in ltrs) 35Weight of C.T (in Kg) 110

CURRENT TRANSFORMER(FOR 33KV)

MANUFACTURED BY- KAPCO Electricals (P) Ltd

POTENTIAL TRANSFORMERS

Purpose:• To step-down the high magnitude of voltage

to a safe value to incorporate Measuring and Protection logics.

• Voltage transformers serve a number of functions in a power system. They are required for the operation of many types of instrumentation and relay protective systems.

CAPACITIVE VOLTAGE TRANSFORMER (CVT)

• Primary voltage is applied to a series of capacitors group. The voltage across one of the capacitor is taken to aux PT. The secondary of the aux PT is taken for measurement and protection.

CAPACITOR VOLTAGE TRANSFORMERMANUFACTURED BY – W.S. Industries (India) Ltd.

MANUFACTURED IN- 1988

Intermediate voltage 20 KVTotal output simultaneously 450 KV

Input maximum 750 VA at 50 deg cel. AmbOperating voltage 220 KV 245 KV (max)

Voltage factor 1.5 50 secTest voltage 1min 460 KV

Impulse withstand voltage 1.2/50 microsec 1050 volt Frequency 50 Hz

HF capacitance 4400 pfPrimary capacitance 4840 pf

Secondary capacitance 48400 pfVoltage ratio 220KV/110Volts

ISOLATOR

• Isolators are used to isolate the circuit when current has already been interrupted. They ensure that current is not switched in to the circuit. Until everything is in the order.

• Isolators are operate on the no load condition. These devices are not the arc quenching devices and they do not have any specific current breaking capacity or current making capacity. In some cases they are used for breaking charging current of transmission line.

CB

Earth S/W

IsolatorIsolator LoadSource

FEATURES OF ISOLATORS

• OPERATES UNDER NO LOAD CONDITION• INTERLOCKED WITH BREAKERS AND EARTHSWITCHES • SHOULD WITHSTAND EXTREME WIND PRESSURES• MOTOR DRIVEN AND HAND DRIVEN• LOCAL AS WELL AS REMOTE OPERATION POSSIBLE• ISOLATES SECTIONS FOR MAINTENANCE• USED TO SELECT BUS BARS• SELECT CT FOR BUS BAR PROTECTION

ISOLATOR(FOR 220 KV)

MANUFACTURED BY – S & S Power switches & gear Ltd

Main design voltage 245 KVCurrent rating 1250 AFrequency 50 HzMotor operation Mechanical Motor voltage 415 V a.cD.C voltage 220 V

Earth switch

INTRODUCTION

• It is connected between the line conductor and earth. Normally it is open and it is close to discharge the voltage trapped on the isolated or disconnected line. When the line is disconnected from the supply end, there is some voltage on the line to which the capacitance between the line and earth is charged. This voltage is significant in hv system. Before commencement and maintance work it is necessary that these voltages are discharged to earth by closing the earthing switch. Normally it is mounted on the frame of isolator.

FEATURES OF EARTH SWITCHES• USED TO GROUND SECTIONS REQUIRED FOR MAINTENANCE• GROUND INDUCTION VOLTAGES• INTERLOCKED WITH BREAKERS AND ISOLATORS• CAN OPERATE FROM LOCAL ONLY• MOTOR DRIVEN AS WELL AS HAND DRIVEN• SAFETY DEVICE Sequence of operation during opening/ closing of a circuitWhile opening: open circuit breaker, open isolator and close earthning switch.While closing: open earthing switch, close isolator and then close circuit breaker

Circuit breaker

THEORY OF CIRCUIT BREAKER• This is the most important switchgear component. It must be able to break and make

normal load current, but above all be able to interrupt short-circuit currents due to faults in the system.

• • The main components of a circuit breaker are the interrupting chamber and the operating

mechanism. Energy is stored in the operating mechanism, and when called upon, this energy is released such that the breaker contacts are forced apart. The

• Arc, now establishing itself between the parting contacts, is then extinguished by high-pressure arc quenching medium blown towards the arc.

• • A circuit breaker is a device used to open and close electrical circuits. Thus, it in some

respect has a similar function to that of a low voltage circuit breaker in one’s home. • In the closed position, a circuit breaker shall be an ideal conductor. That is, when closed,

the circuit breaker shall carry its rated normal current without losses or overheating. In the open position, a circuit breaker shall be an ideal insulator and shall withstand its rated voltage and all nature of over voltages, without a breakdown of either the internal or external insulation.

CLASSIFICATION OF CIRCUIT BREAKERS

• Oil circuit breaker• Air break circuit breaker• Air-blast circuit breaker• SF6 gas circuit breaker• Vacuum circuit breaker

Battery bank

Need of Battery Bank

The battery bank is most dependable source of dc power and is required for following functions:• For closing & tripping of circuit breakers in sub

stations.• For operations of automatic protective devices.• For signalling equipments & remote control

apparatus.• For telephone services and emergency lighting in case

of power plants and sub stations.• For providing dc supply to the PLCC equipments.

Wave trap

Wave trap contains a main coil, lightning arrester and a tuning device. All are connected in parallel. The main coil has an inductance of 0.2

mH to 2.0 mH. This inductance offers high impedance to high frequency (50 KHz to 500 KHz) carrier signals and blocks them here. It does not allow them to enter the power system equipments. However

it offers very low impedance to the power frequency signal.Hence it acts as an insulator of high frequency carrier signal and a

conductor for the power frequency (50 Hz). Since main coil is connected in series with the line current even under fault conditions.

Therefore it is designed from the current rating point of view. The current rating of main coil may be as high as 4000 A. The lightning arrester used to protect the main coil from voltage surges whereas the tuning device is used to block the signals of narrow band carrier

frequency.

PURPOSE

• Wave trap is used for Protection of the transmission line and communication between the Substations.

• VHF signal is transmitted from one end to the another through the same power line.

• Sends inter-trip signal to the other end CBs so that fault can be isolated at the earliest time.

POWER LINE CARRIER COMMUNICATION [PLCC]

• Power line carrier communications (PLCC) refers to the Concept of transmitting information using the electrical power distribution network as a communication channel. This Technology allows a flow of information through the same cabling that supply the electrical power.

BENEFITS

• PLCC integrates the transmission of communication signal and 50/60 Hz power signal through the same electric power cable. The major benefit is the union of two important applications on a single system. The data link appears 'transparent' to the user. Although the devices are connected through the power line; consumers perceive that there is a “separated” link available for data communications.

THE CHALLENGE

Since the power line was devised for transmission of power at 50/60 Hz and at most 400 Hz, the use of this medium for data transmission (especially at high frequencies) presents some technically challenging problems. It is one of the most electrically contaminated environments, which makes it very hostile for transmission of data signals. The channel is characterized by high noise levels and uncertain (or varying) levels of impedance and attenuation. In addition, the line offers limited bandwidth in comparison to cable or Fiber-optic links. Power line networks are usually made of a variety of conductor types and cross sections joined almost at random. Therefore a wide variety of characteristic impedances are encountered in the network. This imposes interesting difficulties in designing the filters for these communication networks