Relay and measurement

1. IN THE NAME OF ALLAH WHO IS THE
MOST BENEFICENT AND THE MOST
MERCIFUL

2. Measurement and Relay
Indications
National T
ransmission and Despatch Company Ltd
PRESENTED BY:
ENGR: SYED GHULAM MUST
AFA
Deputy Manager (Technical)
o/o Chief Engineer TSG (South) NTDC
HYderabad
PCC-OG-136 (31-07-2023 to 08-09-2023)

3. CONTENTS
INTRODUCTION
FUNCTIONS OF PROTECTION SCHEMES
CLASSIFICATION OF PROTECTIVE RELAYS BASED ON
TECHNOLOGY
ANSI STANDARD DEVICE NUMBERS & COMMON
ACRONYMS
MEASURING INSTRUMENTS
AMPEREMETER, VOLTMETER, WATTMETER, POWER
FACTOR METER, FREQUENCY METER
Q&A

4. FUNCTIONS OF
PROTECTION SCHEMES
To sense/detect the fault occurrence and other abnormal conditions
at the protected equipment/area/section.
To operate the correct circuit breakers so as to disconnect only the
faulty equipment/area/section as quickly as possible, thus
minimizing the damage caused by the faults.
To operate the correct circuit breakers to isolate the faulty
equipment/area/section from the healthy system in the case of
abnormalities like overloads, unbalance, undervoltage, etc.
To clear the fault before the system becomesunstable.
To identify distinctly where the fault has occurred.

5. CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
Protective relays can be broadly classified into the following three
categories, depending on the technology they use for their
construction and operation.
1. Electromechanical relays
2. Solid state (static) relays
3. Digital / numerical relays

6. CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
1. Electromechanical relays
 The oldest type of relay.
 First generation of electromechanical relay which came in 1901.
 Operate based on the regulation of mechanical force generated
through the flow of current in windings wounded on magnetic
core.

7. CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
1. Electromechanical relays – thermal relay
- Operates on the principle of
heating effect of electrical
current.
- When the overload condition is
detected, the bimetal strips
bend and allow the trip contact
to energize the trip circuit.
THERMAL RELAY

8. CLASSIFICATION OF PROTECTIVE RELAYS
BASED ON TECHNOLOGY
1. Electromechanical relays – attracted armature relay
- Operates on the principle of
electromagnetic force produced
which attracts the plunger or
hinged armature.
- When the electromagnetic force
exceeds the restraining force, the
moving contact closes due to the
movement of the armature.
Hinged type Plunger type
ATTRACTED ARMATURE RELAY

9. CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
1. Electromechanical relays – induction relay
- Operates on the principle of
electromagnetic induction.
- Operating force is developed
due to the interaction of two
AC flux displaced in time and
space in movable element
(rotor).
INDUCTION RELAY
Induction disc relay Induction cup relay

10. CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
1. Electromechanical relays – balance beam relay
- Operating coil produces operating
torque, whereas restraining coil
produces restraining torque.
- The electromagnetic force of both
coils are in opposition.
- When operating torque exceeds
restraining torque, the movement of
armature closes the contact.
BALANCE BEAM RELAY

11. CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
1. Electromechanical relays
Alstom IDMT earth fault relay Alstom Check Synchronising Relay
EXAMPLES OF ELECTROMECHANICAL RELAY

12. CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
1. Electromechanical relays
ADVANTAGES DISADVANTAGES
 Fast operation and can be reset fast.
 Simple construction.
 Reliable and rugged.
 The values can be easily set
and no programming is
required.
 People can be trained on these relays
easily.
 Have high VAburden thus require high
burden CTs and VTs to operate them.
 Do not have directional feature.
 Affected by the ageing of
components, dust and pollution
resulting in spurious trips.
 Operation speed is limited by the
mechanical inertia of the component.
 One relay can only perform one
function (multifunctioning not
possible).

13. CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
2. Solid state (static) relays
 Due to the advent of electronic devices such as diode,
transistor, ICs, chips etc.
 Second generation of relays.
 Came into operation in 1950s.
 More accurate and higher reliability compared with
electromechanical relays.

14. CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
2. Solid state (static) relays
 The static means the relay has no moving part.
 The semiconductor devices are used for data processing and also
to create relay characteristic.
 Lower relay burden due to no moving parts thus further reduces
the CT/VT requirement.
 Require separate DC power supply.

15. CLASSIFICATION OF
PROTECTIVE RELAYS
BASED ON TECHNOLOGY
2. Solid state (static) relays
EXAMPLE OF STATIC RELAY BLOCK DIAGRAM
Generalized block diagram of static time overcurrent relay
- The secondary current from CT is
rectified, filtered and fed to timing and
curve shaping circuit.
- The output of timing circuit is then
given to level detector which compares
between relay and reference
quantities.
- When the magnitude of relay quantity
exceeds the magnitude of reference
quantity, it generates a voltage signal.
- The voltage signal is then amplified by
amplifier block and fed to tripping
circuit.
- Finally, the tripping circuit generates a
tripping command and send to trip coil
of circuit breaker.

16. CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
GEC Alstom Static Distance Protection Relay GEC Static Differential Protection Relay
EXAMPLES OF STATIC RELAY
2. Solid state (static) relays

17. 2. Solid state (static) relays
CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
ADVANTAGES DISADVANTAGES
 Do not contain moving parts – thus free
from problems such as contact
bouncing, arcing, erosion and friction.
 Significantly less burden on
instrument transformers
(CT/VT).
 Can incorporate variety of functions in a
single unit.
 Quick response and reset action.
 Greater sensitivity can be obtained by using
amplification block.
 Superior characteristic and accuracy.
 Electronic devices are more sensitive
to voltage spike and other transients
that can cause malfunction.
 Require auxiliary DC to operate.
 Has low short time overload capacity.
 The characteristic of electronic devices
are affected by temperature and
ageing of semiconductor devices.
 Costlier compared to electromechanical
relay.
 Require highly trained persons to service
static relay which has complex protective
functions.

18. 3. Digital / numerical relays
 Entered the market around 1980s.
 Based on microprocessors and microcontrollers.
 Instead of using analog signals, this relay
analogue quantities into digital signals.
converts all measured
 Microcontrollers are used in replacement of analogue circuits used in
static relays.
 Digital / numerical relays introduce Analogue to Digital Convertor (A/D
conversion) of all measured analogue quantities and use a
microprocessor to implement the protection algorithm.
CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY

19. 3. Digital / numerical relays
CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
BASIC BLOK DIAGRAM OF
A DIGITAL / NUMERICALRELAY
Anti aliasing
filter

20. 3. Digital / numerical relays
CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
ABB digital distance protection relay SEL Transmission Protection System
Siemens Transformer differential
protection
EXAMPLES OF DIGITAL OR NUMERICAL RELAY

21. 3. Digital / numerical relays
CLASSIFICATION OF
PROTECTIVE RELAYS BASED
ON TECHNOLOGY
ADVANTAGES DISADVANTAGES
 Various functions such as multiple setting
groups, programmable logic, events
recording and oscillography.
 Has the ability of self monitoring and self
testing.
 Ability to communicate with other
relays and control computers.
 Cost per function is lower.
 User can develop their own logic schemes.
 Less burden on instrument transformers.
 Less panel space because it can provide
many functions in a single relay.
 Short life cycles due to fast advancement in
microprocessor and microcontroller technology.
 Because it can provide many functions in a
single relay, all the functions will share a
common failure. For example, failure of a
power supply or an input signal processor
may disable the entire relay functions.
 Not immune to electrical transients
such as electromagnetic interference
(EMI) and radio frequency interference
(RFI).
 The increased number of settings may
pose problems in managing the
settings and in conducting functional
tests.

22. ANSI STANDARD DEVICE
NUMBERS & COMMON
ACRONYMS
The ANSI (American National Standards Institute) standard
device numbers denote what features a protective device
supports (such as a relay or circuit breaker).
The device numbers are used to identify the functions of
devices shown on a schematic diagram.
One physical device may correspond to one function number or
may have many function numbers associated with it, such as
for numerical protective relay.
Suffix and prefix letters may be added to further specify the
purpose and function of a device.

24. BASIC
MILLIAMMETER
Connected in series with the circuit so that the whole
electrons of measurand current passes through the
ammeter
.
The power loss occurs in ammeter because of the
measurandcurrentandtheirinternalresistance.
Theammetercircuithaslowresistancesothatthe small
voltagedrop occursinthecircuit.
Theresistanceof theammeteriskeptlowbecauseof the
tworeasons:
•The whole measurand current passes through
the ammeter
.
•Thelowvoltagedrop occursacrosstheammeter
.

25. • Thefollowingarethetypesof an
ammeterregardingconstruction:
1.Permanentmovingcoilammeter
.
2.Movingiron ammeter
.
3.Electro-dynamometerammeter
.
4.Rectifiertype ammeter
.
• By the current, the
ammeter categoriesintotwo
types.
1.ACammeter
2.DCammeter

26. BASIC DC
VOLTMETER

27. WATT METER
• A WATTMETER IS USED FOR
MEASURING THE WATTS IN THE
CIRCUIT.
• .

28. WATT METER
• THE INTERNAL CONSTRUCTION OF A WATTMETER IS SUCH THAT IT CONSISTS OF TWO COLS. ONE
OF THE COIL IS IN SERIES AND THE OTHER IS CONNECTED IN PARALLEL. THE COIL THAT IS
CONNECTED IN SERIES WITH THE CIRCUIT IS KNOWN AS THE CURRENT COIL AND THE ONE THAT
IS CONNECTED IN PARALLEL WITH THE CIRCUIT IS KNOWN AS THE VOLTAGE COIL.
• WHEN THE CURRENT PASSES THROUGH THE CURRENT COIL, IT CREATES AN ELECTROMAGNETIC
FIELD AROUND THE COIL. THE STRENGTH OF THIS ELECTROMAGNETIC FIELD IS DIRECTLY
PROPORTIONAL TO THE AMOUNT OF CURRENT PASSING THROUGH IT
• IN CASE OF DC CURRENT, THE CURRENT IS ALSO IN PHASE WITH ITS GENERATED
ELECTROMAGNETIC FIELD. THE VOLTAGE IS DROPPED ACROSS THE POTENTIAL COIL AND AS A
RESULT OF THIS COMPLETE PROCESS, THE NEEDLE MOVES ACROSS THE SCALE. THE NEEDLE
DEFLECTION IS SUCH THAT IT IS ACCORDING TO THE PRODUCT OF THE CURRENT PASSING AND
THE VOLTAGE DROPPED, THAT IS, P = VI.

29. POWER FACTOR METER
• THE POWER FACTOR IS DEFINED AS
THE RATIO OF THE ACTIVE POWER (P)
AND VOLT-AMPERES. THE ACTIVE
POWER IS THE REAL POWER WHICH
IS ASSUMED IN AN AC CIRCUIT,
WHEREAS VOLT-AMPERES IS THE
APPARENT POWER WHICH IS
PRODUCED IN THE CIRCUIT WHEN
THE WAVES OF VOLTAGE OR CURRENT
ARE NOT IN PHASE.

30. POWER FACTOR METER
• THE POWER FACTOR OF THE TRANSMISSION LINE IS MEASURED BY DIVIDING THE PRODUCT
OF VOLTAGE AND CURRENT WITH THE POWER. AND THE VALUE OF VOLTAGE CURRENT AND
POWER IS EASILY DETERMINED BY THE VOLTMETER, AMMETER AND WATTMETER
RESPECTIVELY. THIS METHOD GIVES HIGH ACCURACY, BUT IT TAKES TIME.
• THE POWER FACTOR OF THE TRANSMISSION LINE IS CONTINUOUSLY CHANGED WITH TIME.
HENCE IT IS ESSENTIAL TO TAKE THE QUICK READING. THE POWER FACTOR METER TAKES A
DIRECT READING, BUT IT IS LESS ACCURATE.
• THE POWER FACTOR METER HAS THE MOVING SYSTEM CALLED POINTER WHICH IS IN
EQUILIBRIUMWITH THE TWO OPPOSING FORCES. THUS, THE POINTER OF THE POWER
FACTOR METER REMAINS AT THE SAME POSITION WHICH IS OCCUPIED BY IT AT THE TIME
OF DISCONNECTION.

31. FREQUENCY METER
• FREQUENCY METERS ARE THE INDICATING
INSTRUMENTS WHICH MEASURES THE
FREQUENCY OF ELECTRICAL ENERGY. THIS
ELECTRICAL ENERGY MAY BE AC OR DC OR IN A
FORM OF VARIOUS SIGNALS OR WAVES
PRODUCED BY VARIOUS CIRCUITS
• THE VARIATIONS IN AN ELECTRIC
CURRENT DRAWN
BY INDUCTIVE AND NON-INDUCTIVE
CIRCUITS ARE CONNECTED IN
PARALLEL. THE CURRENT FLOWS FROM
THESE CIRCUITS AND THE CURRENTS OF
BOTH CIRCUITS CHANGES THEIR VALUE
THEN THE FREQUENCY IS MEASURED.

32. FREQUENCY METER
Types of Frequency Meters
Frequency meters are of three types which are as follows:
•Moving Iron Frequency Meter
•Electrodynamic Frequency Meter
•Vibrating reed Frequency Meter

33. Q & A
Session