Measurement and Relay Indications download.pptx

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

Measurement and Relay
Indications
National Transmission and Despatch Company Ltd
PRESENT
ED BY:
ENGR: SYED GHULAM MUSTAFA
Deputy Manager (T
echnical)
o/o Chief Engineer TSG (South) NT
DC HYderabad
PCC-OG-140

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

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 becomes unstable.
 To identify distinctly where the fault has occurred.

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

 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.

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

CLASSIFICATION OF PROTECTIVE RELAYS
BASED ON TECHNOLOGY
1. Electromechanical relays – attracted armature relay
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

1. Electromechanical relays – induction relay
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

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

Alstom IDMT earth fault relay Alstom Check Synchronising Relay
EXAMPLES OF ELECTROMECHANICAL RELAY

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 VA burden 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).

 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.

 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.

RELAYS
BASED ON TECHNOLOGY
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.

GEC Alstom Static Distance Protection Relay GEC Static Differential Protection Relay
EXAMPLES OF STATIC RELAY

 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.

 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.

BASIC BLOK DIAGRAM OF
A DIGITAL / NUMERICAL RELAY
Anti aliasing
filter

ABB digital distance protection relay SEL Transmission Protection System
Siemens Transformer differential
protection
EXAMPLES OF DIGITAL OR NUMERICAL RELAY

 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.

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.

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
measurand current and their internal resistance.
The ammeter circuit has low resistance so thatthe small
voltage drop occurs in the circuit.
The resistance of the ammeter is kept low because of the
two reasons:
•The whole measurand current passes
through the ammeter
.
•The low voltage drop occurs across the ammeter
.

• The following are the types of an
ammeter regarding construction:
1.Permanent moving coil
ammeter
. 2.Moving iron
ammeter
.
3.Electro-dynamometer ammeter
.
4.Rectifier type ammeter
.
• By the current, the
ammeter categories into two
types.
1.AC ammeter
2.DC
ammeter

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

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.

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.

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 EQUILIBRIUM
WITH 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.

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.

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

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