Area of vulnerabilty

AREA OF VULNERABILITY FOR
PREDICTION OF VOLTAGE
SAGS
PROPOSED BY
1) Prasad Joshi
2) Pavan Deore
K K WAGH Institute of Engineering Edu
& Research, Nashik

“Vulnerability”
 Dictionary meaning
the state of being vulnerable or
exposed;
“Vulnerability”
exposed to the possibility of being
attacked or harmed, either physically
or emotionally.
Another word is susceptibility

What is “Area of Vulnerability”?
 The vulnerability is the ability of a
network continuing to provide key
services during random failures or
intentional attacks.
 Vulnerability area is considered the
zone of a distribution network in
which short-circuit causes a voltage
dip, with the specified value, or an
interruption of short duration.

For what Power System is
vulnerable?
 The important factors to which
distribution systems are vulnerable
include voltage sags, swells &
momentary disturbances

Power Quality Terminologies
Voltage Sags:
A voltage sag, also known as dip, is the decrease in rms voltage between
0.1 and 0.9 p.u at the power frequency for duration between 0.5 cycles to
1 min.
Voltage Swell
Voltage Swells are momentary (typically a few milliseconds to a few
seconds duration) over-voltage conditions which can be caused by such
things as a sudden decrease in electrical load or a short circuit occurring
on electrical conductors.
Harmonics:
Power system harmonics are integer multiples of the fundamental power
system frequency. Power system harmonics are created by non-
linear devices connected to the power system. High levels of power
system harmonics can create voltage distortion and power quality
problems.
Harmonics in power systems result in increased heating in the equipment
and conductors, misfiring in variable speed drives, and torque pulsations
in motors.

Impacts of Power System
distortions
The networks of power system, often called power grids, have been
regarded as one of the most important infrastructures whose security
should be paid more and more concern. However, in recent years, several
large blackouts occurred in India, which have resulted in direct loss up to
crores of rupees.
Duration of voltage dips or short interruptions is determined by the protection time
response. The incidents occurred in distribution networks are eliminated by the
protection of the affected equipments. Meanwhile, in a large area of distribution
networks, the voltage of the affected phase (phases) decreases to values between 1
and 0 p.u., according to the “electrical distance” from the place where the incident
took place.

Impacts of Power System
distortions
Wide-area interruptions in the electricity supply have severe impacts on
society’s critical functions, and there is a need for tools and methods to
structure and analyze events, causes and consequences.
The networks of power system, often called power grids, have been
regarded as one of the most important infrastructures whose security
should be paid more and more concern. However, in recent years, several
large blackouts occurred in India, which have resulted in direct loss up to
crores of rupees.
Duration of voltage dips or short interruptions is determined by the protection time
response. The incidents occurred in distribution networks are eliminated by the
protection of the affected equipments. Meanwhile, in a large area of distribution
networks, the voltage of the affected phase (phases) decreases to values between 1
and 0 p.u., according to the “electrical distance” from the place where the incident
took place.

Can we stop it???
•NO
•But still voltage sag can occur & spread hence we need to
provide preventive solutions.
•To provide preventive solutions we need to recognize the
area of vulnerability
“The analysis is usually done by steady-state or time domain simulations using
power system analysis software. Time-domain simulation is carried out to determine
the voltage sag
magnitude variation from the point of its occurrence until it returns to its normal
state. It is also used for determining the voltage sag duration. This type of analysis is
very useful for equipment sensitivity studies. However, it needs a very high computing
capability and other supporting tools to be able to simulate a large and practical power
system. Steady state simulation using load flow and short circuit analyses can give
reasonable and adequate information for utility as well as customers to understand and
take necessary steps to overcome voltage sag problem. Information such as area of
vulnerability and phase angle jump are some of the information obtained from steady
state simulation. It does not need high computing power even for a large power
system.”

Voltage Sag Analysis
Methodolgy
Step Methods
Identification of threats and
unwanted events
Check lists and expert interviews
Bow-tiemodel
Probabilistic safety analysis
Contingency analysis
Graph/ network theory
Causal analysis Fault analysis
FMEA/ FMECA
Fault tree analysis
Expert judgement
Consequence analysis Event tree analysis
Power flow/ dynamic contingency analysis
Monte Carlo simulation
Graph/ network theory
Expert judgement
Discrete event simulation
Risk and vulnerability
evaluation
Cost benefit
Risk matrix/ diagram
Multi criteria decision analysis

In Steps
The method used in the voltage sag analysis is describe as below :
 1. Choose a network for voltage sag analysis.
 2. Create a model for the network.
 3. Solve the base case load flow on all the three phases
simultaneously. Record the voltage magnitude and angle at each node
and for each phase. The recorded data will be the pre-sag values of
voltage magnitude and angle.
 4. Create dummy nodes and lines to represent fault points along the
lines for sliding fault analysis as shown in Fig. 1. Fig. 1 Sliding Fault
Analysis
 5. For single line to ground (SLG) fault simulation, create SLG faults for
phase A at various points in the network and record the value of its
voltage magnitude and angle for all the nodes.
 6. Repeat step (4) for phase B and C.

 7. For three phase to ground (TPG) fault simulation, create TPG faults
at various points in the network and record the values of voltage
magnitude and angle for all nodes.
 8. For multiple sliding faults simulations, create multiple faults as
shown Fig. 2 in the network and record values of voltage magnitude
and angle. The values recorded in steps (4) till (8) are considered as
voltage values at sag conditions. Voltage sag
 magnitude is the ratio of these voltage magnitude to rated voltage for
that node. And the phase jump is the difference in angle of pre-sag and
during sag.
 9. Create voltage sag prediction table based on historical data and
voltage sag simulation results. The sliding fault is normally simulated
by manually removing the line/s on which the sliding fault analysis is to
be applied. Next, create dummy nodes along the line/s. Then connect
all the nodes with lines that the
 same properties as the one removed (see Fig. 1). However, this
process were automated in this develop software with user only specify
the line/s and number of fault analysis locations. Fault/s then applied
at the dummy node/s.

Case Study
 EDDY CURRENT SEPARATOR
 COMPRESSED INTO BLOCKS
 LOADED TO FURNACE
 HYDROGEN REMOVAL
spectroscopic analysis
 APPLICATIONS

How this Case study helps in
determining AoV.

Conclusion
 Why AoV is Important
 We studied AoV
 We are choosing this topic in our PG
Studies

Area of vulnerabilty

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