Transcript Reasons for non operation

Operational Experience of system Protection
Scheme of Talcher – Kolar HVDC Link
MISSION OF POWER SYSTEM ENGINEERS
To provide
Reliable,Secured,and stable power supply
AT
Least possible cost
AND
Maximizing profit to all Stake holders
Security Monitoring
Normal
Restoration
Preventive
Control
Restorative
Alert
Emergency
Control
In extremis
Emergency
Why System protection Schemes
• Changing rules of operating electric power
– Due to Deregulation of Electricity market
– Seeking better Profits by
• Optimising maintenance
• Over utilising the asset
• System Operators have to cope up with following “mores” resulting
in accommodating transactions reducing the security margin
–
–
–
–
–
Capacity and complexity of the power grid
Inter-regional power exchange
Information to be handled
Uncertainty in operating conditions
Frequency of fault to be a trigger
• System Operator has to manage the contingencies in addition to
handling above Mores and maintain integrated operation. System
protection Schemes is a tool to achive this
System Protection Scheme Definition
• a protection scheme that is designed to detect a
particular system condition that is known to cause
unusual stress to the power system and to take some
type of predetermined action to counteract the observed
condition in a controlled manner. In some cases, SPSs
are designed to detect a system condition that is known
to cause instability, overload, or voltage collapse. The
action prescribed may require the opening of one or
more lines, tripping of generators, ramping of HVDC
power transfers, intentional shedding of load, or other
measures that will alleviate the problem of concern.
Common types of line or apparatus protection are not in
the scope of interest here”
Characteristic of SPS
•
•
These protections are also known by other names depending on the
originator like
–
Special stability controls
–
Dynamic security controls
–
Contingency arming schemes
–
Remedial action schemes
–
Adaptive protection schemes
–
Corrective action schemes
–
Security enhancement schemes
Depending on the type of the problem, action such as tripping of
generators, intentional islanding of the system at predetermined
locations, tripping of loads will be taken.
Characteristic of SPS
•
•
SPS are dynamic security control systems and are
designed to control power system stability in case
where the uncontrolled response is likely to be more
damaging than the controlled response.
SPS are devised by off –line analysis as opposed to
on – line real time control. The reason behind being
power system response is too fast to allow sequential
control system logic. Involvement of a grid operator
(human intervention for corrective action) should be
kept to minimum contrary to SCADA/EMS (i.e.
dispatchers’ actions and maintenance effort).
Types of Power system instability and the
corrective actions
• Frequency Instability – The power system frequency
going beyond operating limits
• Tripping of generators
• Fast generation reduction through fast-valving or water
diversion
• HVDC power transfer control
• Load shedding
• Controlled opening of interconnection to neighboring
systems to prevent spreading of disturbance
• Controlled islanding of local system into separate areas
with matching generation and load
• Voltage Instability - Inability of the power system to
maintain steady acceptable voltages at all buses in the
system
• Change of the generator voltage set point
• Automatic shunt switching
• Control of series compensation
• Blocking of Tap Changer of transformers
• Under voltage load shedding
• Transient Angular Instability - Inability of the system to
maintain synchronism
– Braking resistor, FACTS devices etc.
– Reducing the mechanical power driving the generator:
– Fast-valving, disconnection of the generator etc.
• SR grid Over view
SR grid Over view
SR grid Over view
First Stage Logic Implementation
First stage Logic
MODE OF OPERATION
POWER LEVEL FOR GENERATING INTERTRIP SIGNAL
MONO POLAR
>400 MW AND THE POLE TRIPS
IF BOTH POLE ARE CARRYING > 800 MW EACH AND
ANY ONE POLE TRIPS
IF POWER FLOW ON EACH > 200 MW AND BOTH POLE
TRIP
BI-POLAR
IF EACH POLE WAS CARRYING POWER IN THE
RANGE OF 400-800 MW AND ONE POLE TRIPS,
TRIP IS EXTENDED IF AFTER A DELAY OF 2
SECONDS THE POWER OF SURVIVING POLE IS
LESS THAN 600 MW.
List of stations to which the trip signals are sent and the quantum of connectedLoad
Station
Name
Yeraguntala
Connected
Load
150
Kolar
Hoody
250
Salem
Sriperambadur
Hosur
100
100
100
Performance Analysis of the Stage I Scheme
Performance
No. of times System Protection Scheme
Expected to
Operate
Operated
correctly
29
18
Failed to Operate
11
No of times
SPS
operated
when not to
operate
7
Analysis of Improper operation
•
Mal operations
– On seven occasions the scheme operated when not required to operate
due to failure of the HVDC measuring equipment like Optodyne/control
errors(During initial period of Operation) due to which the power flow by
the healthy pole could not be compensated with in two seconds after one
pole trip
Reasons for non operation
Number of Non
Operations
Reasons
Five
When one pole trips on line fault the surviving pole goes to
150MW as per the present control scheme and this type of power
ramp down is very slow(>>2sec). Since the logic checks the power
loss only after 2 seconds of the incident, the logic failed to operate.
This has been taken care in the Stage –II SPS logic development
by introducing a line fault signals.
One
During the initial stages of the logic development, checking the
monopolar/Bipolar status was missed in the logic. This problem
was later rectified
One
Due to communication failure between Talcher and Kolar the
HVDC system went in to shutdown mode and the power was
ramped dowm very slowly .this was not envisaged in the logic
design
Four
The power level signals were derived from HVDC control which
was changing only in steps (bit form). Therefore decisions were
influenced by the power levels in specified steps which at times,
could not detect the actual loss of power of more than 400MW.
This has been taken care in the Stage –II SPS logic development
Reasons for going in for revisions in the scheme
•
•
•
•
Increased Power flow through Talcher –Kolar HVDC link
– more quantum of load shedding
– Non availability of sufficient quantum of sheddable loads around Kolar
To prevent excess load shedding
– graded inter trip signals corresponding to the power loss were required
To improve upon the deficiency noticed in stage I
Implementation like
– To take Analog signals for the pole power status instead of bit status in
the earlier logic
– Providing Two trip signals for different power loss
– To consider line faults in the logics
Logic of Presently improved SPS
SIGNAL A
REDUCTION IN POWER
> 500&<1000MW
TRIP SIGNAL 1
OR
POWER FLOW
>1000&<1500MW
AND
DC LINE
FAULT
AND
POWER FLOW > 1500MW
TRIP SIGNAL 2
AND
OR
REDUCTION IN POWER >
1000MW
SIGNAL B
Substations to which Trip Signal I is sent and the expected relief
STATE
A.P
Kar
SUBSTATIONS
Chinakampalli
RELIEF
150MW
Kolar ICT
250MW
Hoody
Hosur
TN
REMARKS
Signal through wide band.
Through local pilot wiring
Through PLCC
Through PLCC
Sriperumbudur
300MW
Signal through wide band.
Salem
Substations to which Trip Signal II is sent and the expected relief
STATE
SUBSTATIONS
RELIEF
REMAR
K
Signal
will be
sent
through
wide
band
A.P
GTY Switching Stn, Ananthapur Somayajulapalli
Kurnool
200
Kar
Somanahalli
200
Kerala
Trichur North , Kozhikode
200
TN
Madurai,Karaikudi,Thiruvarur,Trichy230 Ingur
200
Performance of the Scheme
FREQUENCY DIP DURING KOLAR HVDC TRIPING AND DURING SIMHADRI GENERATION LOSS
50.1
TAL-KOL TRIP ON15-09-06 AT 16:52 HRS
LOSS IS 1887 MW
49.9
FREQ IN HZ
49.7
49.5
49.3
49.1
SIMHADRI GEN LOSS OF
APPROX 950 MW ON 16-01-07
AT 1812 HRS
48.9
48.7
48.5
T-30 Minutes
T-25 Minutes
T-20 Minutes
T-15 Minutes
T-10 Minutes
Time
T-5 Minutes
T=0 Minutes
T+5 Minutes
Performance of the Scheme
No. of times System Protection Scheme
Expected
to Operate
Operated
correctly
9
8
Failed to
Operate
No of times SPS operated when
not to operate
1
2
Details of Improper operations
Improper
operation
No.of
operation
Reasons
Non Operation 1
Due to Problems in HVDC controls and matter
referred to the supplier
Mal
operations
Problems in HVDC controls and the logic Same has
been rectified
2
Due to fluctuations in power flow during tripping of
converter transformer