protective relaying for der - cscos. · pdf fileprotective relaying for der ... ♦voltage...
TRANSCRIPT
Protective Relaying for
DERRogerio Scharlach
Schweitzer Engineering Laboratories, Inc.
Basking Ridge, NJ
Overview
• IEEE 1547 general requirements to be
met at point of common coupling (PCC)
• Distributed resource (DR) response to
area electric power system (EPS)
abnormal conditions
Overview
• Distributed generation (DG) impact on
distribution feeders
• Real Life Operation of DR Interconnection
Protection
• Introduction to Symmetrical Components
IEEE 1547 General Requirements
to Be Met at PCC
• Voltage regulation
• Integration with area EPS grounding
• Synchronization
• Inadvertent energization of area EPS
• Monitoring provisions
• Isolation devices
• Interconnection integrity
DR Response to Area EPS
Abnormal Conditions
• Faults
• Reclosing
• Voltage excursions
• Frequency excursions
• Loss of synchronism
• Reconnection to area EPS
DR Response to Area EPS Faults
DR unit shall cease to energize area EPS
for faults on area EPS circuit to
which it is connected
DR Response to Area EPS Reclosing
DR shall cease to energize area EPS
circuit to which it is connected prior to
reclosing by area EPS
DR Response to Voltage Excursions
• Voltage parameters are to be met at PCC
• Interconnection system responds to rms
or fundamental voltage
♦ Phase to phase
♦ Phase to neutral
Voltage Range (% of base voltage) Clearing Time (s)
V < 50 0.16
50 ≤ V ≤ 88 2.00
110 ≤ V ≤ 120 1.00
V ≥ 120 0.16
DR Response to Frequency Excursions
DR shall cease to energize area EPS when
system frequency is in particular range
DR Size Frequency Range (Hz) Clearing Time (s)
≤ 30 kW> 60.5 0.16
< 59.3 0.16
> 30 kW
> 60.5 0.16
< 59.8 to 57.0
(adjustable)
0.16 to 300
(adjustable)
< 57.0 0.16
DR Response to Loss of Synchronism
• In this case, DR response
♦ Applies only to synchronous generators
♦ Is primarily a risk to generators
• Standard addresses this condition as being
of concern only if it results in voltage
fluctuations that violate flicker limitations
DR Reconnection to Area EPS
• Reconnection is delayed up to 5 minutes
after area EPS steady-state voltage and
frequency are restored
• Ranges include
♦ Frequency – 59.3 to 60.5 Hz
♦ Voltage – see ANSI C84.1-1995, Table 1
Power Quality
• Limitation to dc injection
• Limitation of flicker induced by DR
• Harmonics
Islanding
• Unintentional
• Intentional
DG Impact on Distribution Feeders
• Increased fault duty
• Unintentional islanding
• Relay desensitization
• Nuisance tripping
• Automatic reclosing
• Voltage regulation and flicker
• Ferroresonance
Increased Fault Duty
• Is caused by addition of generating sources
and rotating machinery of considerable size
• Affects capability of equipment to carry and
interrupt fault currents
• Requires both local and area EPS
equipment ratings to be reevaluated
Unintentional Islanding
• Occurs when portion of area EPS and DR
become electrically isolated from rest of area
EPS and DR continues to energize island
• Should be avoided for two major reasons
♦ There is potential for negative effects on voltage,
frequency, and power quality
♦ Islanded generator complicates both automatic
reclosing and manual switching
Relay Desensitization
• Available short-circuit current increases with
addition of DR
• Short-circuit current splits between
substation and DR
• Substation short-circuit contribution can be
significantly reduced when compared with
value before addition of DR
Relay DesensitizationFault Current Distribution Without DR
323
R1
R2Substation
F1
Three-Phase 3I0
323 A 198 A
198
Relay DesensitizationFault Current Distribution With DR
199
R1
R2Substation
F1Three-Phase 3I0
199 A 24 A
24
200
246
Substation
Three-Phase 3I0
200 A 246 A
DR 399
270
DR
Nuisance TrippingWithout DR
762
R1
R2Substation
F2
Three-Phase 3I0
762 A 616 A
“616”
Nuisance TrippingWith DR
762
R1
R2Substation
Three-Phase 3I0
762 A 616 A
“616”
768
“0”
Substation
Three-Phase 3I0 – 3E0
768 A 0 A – 0.729 pu
DR
F2
3E0
1530
“616”DR
Operation for Fault in Adjacent Zone
SYS
DR
1
2
3
ISYS
ISYS + IFAULT
IFAULT
IFAULT
Automatic Reclosing
• DR should be disconnected before open
interval expires
♦ By interconnection protection (81U, 81O, 59, 27)
♦ By DTT
• Minimum open or dead time to allow arc
deionization and to avoid restrike is
Automatic Reclosing
• If DR can form sustainable island when
separated from system, restoration
becomes issue
• Utility feeder breaker has to be equipped
with synchronism-check element and / or
live-bus and dead-line logic
• OR combination of both elements works as
permissive for reclosing utility feeder breaker
Automatic ReclosingClose Permissives
• Feeder and bus are in synchronism
• Utility bus is hot and line is dead
DR
Utility
Bus
Live Bus /
Dead Line or
Synchronism
3
3
Multifunction
Relay
C T
1
Temporary
Fault
Real Life Operation of DR
Interconnection Protection
PVArray
IsolationTransformer
NeutralGrounding
Reactor
I VY VZ
Pole-mountedRecloser
Recloser Control
59G
51P
51G
275981
Ø-G Fault
Simplified Single-Line Diagram
380 Vac 13,800 Vac
T C
OverheadDistribution
Feeder
Recloser Control Simplified Trip Logic
27-1
27-2
59-2
59-1
81-1
81-2
81-3
59G
51P
51G
OR
OR
OR
TRIP
RECLOSER
Relay Settings
Element Setting Delay Description
27-1 50% 108.33 ms Definite time undervoltage level 1
27-2 88% 1.950 s Definite time undervoltage level 2
59-1 110% 950 ms Definite time overvoltage level 1
59-2 120% 108.33 ms Definite time overvoltage level 2
81-1 57 Hz 78.95 ms (@ 57 Hz) Definite time underfrequency level 1
81-2 58.5 Hz 102.6 s (@ 58.5 Hz) Definite time underfrequency level 2
81-3 60.5 Hz 74.38 ms (@ 60.5 Hz) Definite time overfrequency
59G 8,200 V 1.33 s Definite time residual ground overvoltage
51P 60 A NA Inverse time phase overcurrent
51G 19.8 A NA Inverse time residual ground overcurrent
Relay Underfrequency Settings
Feeder Fault (C-Ground)
Undervoltage Element Pickup Time
15.62 ms
Undervoltage Element Time Delay
108.33 ms
Recloser Interruption Time
17.71 ms
Total Clearing Time
141.66 ms
Introduction to Symmetrical
Components
• The solution of balanced multi-phase
systems can be accomplished using single-
phase methods
• The method of symmetrical components
allows unbalanced multi-phase systems to
be solved using single-phase methods.
♦ Introduced in 1918 by C.L. Fortescue
Insight
“… it is shown that unbalanced problems can be
solved by the resolution of the currents and
voltages into certain symmetrical relations. When
the constants are symmetrical, that is, when the
system viewed from any phase is similar, then the
symmetrical components of currents do not react
upon each other so that it becomes possible to
eliminate the mutual relations with their attendant
complication in the solution of the problems.”
—C.L. Fortescue
Decomposition of an Unbalancedd
System
Symmetrical Components as a
Function of Phase Quantities
Phase Quantities as a Function of
Symmetrical Components
Phase-to-Ground Fault
Two-Terminal System
+
-
Zero Sequence Network During the Fault
Z0S Z0DR
Z0TR
H
H0
3 x ZN
V0Z
N0
X
I0DR= 0
ΔV0 = I0R* (3 x ZN + Z0TR)
CLOSED CLOSED
CB R
I0S≠ 0
I0S + I0R |V0Z| before trip = 2400 V < 2,735 V (pick up)|V0Z| after trip = 3200 V > 2,735 V (pick up)
ΔV0
Residual Ground Overvoltage
Sample DER Interconnected Through
a Delta/ Wye Transformer
PVArray
IsolationTransformer
I VY VZ
Pole-mountedRecloser
Recloser Control
59G
51P
51G
275981
Ø-G Fault
Simplified Single-Line Diagram
T C
OverheadDistribution
Feeder
Z1S
Z1L
Z1DR
Z1TR
Z2S
Z2L
Z2DR
Z2TR
Z0S
Z0L
Z0DR
Z0TR
CB
I1S= 0
I2S= 0
I0S= 0
I1DR= 0
I2DR= 0
I0DR= 0
I0R= 0
V2
V1
V0
E
What is the
3V0 at the
Recloser
Location
After Utility
Separation?
OPEN
OPEN
OPEN
CLOSED
CLOSED
CLOSED
CB
CB
R
R
R
H
X
H0
Conclusions
• There are several requirements to be met
by DR at PCC location
• DR has to respond to abnormal conditions
of area EPS
• Addition of DR to distribution feeder affects
its protection, voltage regulation, fault duty,
reclosing scheme, and so on
Conclusions
• Event report analysis is a great tool to
validate DER interconnection protection
settings
• Unbalanced phasors can be broken down
into their symmetrical components
• Symmetrical components allow the use of
simple single-phase calculations for
analysis of unbalanced systems
• The resultant symmetrical components can
be recombined into the phase components
Questions?
Questions to the audience
• Please provide 3 examples of DR impacts
on distribution feeders.
• Please provide 3 examples of area EPS
abnormal conditions that the DR has to
respond to.
• Can a DR immediately reconnect following
a successful feeder restoration? If not, how
long is the qualifying time delay? What are
the quantities monitored during the
qualifying time delay?
Questions to the audience
• According to the theory of Symmetrical
Components, an unbalanced set of currents
can be decomposed in three other
components. What are these components?
• How are the sequence networks
interconnected to represent a phase-to-
ground fault?