HW06 EE6560 Power System Protection 1
Do 12.47kV distribution protection and coordination. The HW06 ASPEN model, coordination summary table,
and an excerpt from Ameren PS-50 are on Canvas as your starting point. The model already has the network
model, a Recloser with settings, Grocer customer 480V
eaker settings, and Ameren 14G standard 12.47kV
feeder device 51 and 51N settings. You are allowed to change the 12kV 51 and 51N settings and the Recloser
type & size though you must explain your reasoning.
1. Please specify fuses at Point M, Grocer high side (HS), and Point P. Refer to completed coordination
table and TCC to explain. (30 points)
2. Choose the 34.5/12.47kV substation main
eaker device 51 and 51N types, CT ratio, and specify
settings. Refer to completed coordination table and TCC to explain. (50 points)
3. Simulate the required faults and complete the coordination table; (you may need separate phase and
ground coordination tables.) (40 points)
4. Provide PDF of Time-Cu
ent Curves (TCC) for (30 points)
a. Grocer transformer damage curve, fuse, and LS
eaker settings
. Feeder phase protection
c. Feeder ground protection
5. Criteria:
a. In general our minimum Detection Margin = 1.5 (with 2 prefe
ed), and minimum Load Margin
is 1.15, and substation relay minimum Coordinating Time Interval (CTI) = 0.3 seconds.
. PS-50 provides feeder protection and coordination criteria.
c. Strive to minimize total clearing times.
Paul Nauert 3/6/2023
HW06 Coord summary
# Protective Device Load Cu
ent toward Protection Zone Load (A) MTO (A) Load margin Fault type Min EOL Bolted Fault Detection Margin Smallest upstream device Upstream CTI (sec) Largest downstream device Down-stream CTI (sec) Notes
Main 51M Feeders Substation bus 1500 N/A Fdr Dev 51F
Fdr Dev 51F Point M Substation
eaker to Recloser 483 600 1.24 ph-ph 1478 2.46 Main
eaker recloser ph-ph EOL shown as example
Point M __ fuse Velda Point M-Velda 122 Fdr Dev 51F 65T fuse
Grocer HS fuse Grocer new load 12.47kV ∆ / 480V Y 1500kVA transformer 62 Fdr Dev 51F 480V panel main
Recloser with 2 Fast & 2 Slow curves Point P Recloser to Point P 135 Fdr Dev 51F Point P fuse
Point P tap fuse Bus S Point P to Bus S 55 reclose
Load amps include the new grocery store being added at Point M
All at nominal 12.47kV, except Grocer Low Side (LS) is 480V.
CTI means Coordinating Time Interval in seconds
Min EOL means the minimum bolted fault cu
ent at the End Of Line, i.e. the end of the protected zone.
Date DISTRIBUTION FEEDER PROTECTION
Standard Revision
PS-50 4
12/12
Electrical Distribution Design Standard
Sheet
12 of 64
4.0 PROTECTIVE DEVICE APPLICATION
The criteria / guidelines for protective device application on distribution circuits are listed as
follows:
1) The protective device voltage rating must meet or exceed the system operating voltage.
2) The protective device inte
upting capability must exceed the maximum bolted fault
cu
ent (3-phase or phase-ground) at the point of application.
3) The protective device must be able to detect minimum end-of-line bolted faults within its
zone of protection with a margin of 1.5 or greater. A margin of 2.0 or greater is
prefe
ed.
4) The protective device must coordinate with upstream and downstream protective devices.
Lock out coordination must be achieved when two protective devices are connected in
series however; trip coordination may or may not be achieved.
5) The protective device must be able to ca
y maximum continuous loads without damage
or false tripping. Protective device application is for fault isolation, not overload
protection.
6) The protective device must be able to ca
y load during contingency conditions without
damage or false tripping. Contingency conditions include cold-load pickup and circuit
switching.
Examples of protective device application on various types of distribution circuits are provided
in Section 8.0.
4.1 Fuse Application
Fuse voltage rating should meet or exceed the system operating voltage.
Fuse symmetrical inte
upting rating should exceed the maximum bolted fault level at the point
of application. In areas near 4kV substations, the inte
upting rating of T-link fuses may be
exceeded. In these situations, SMU-20, SM-4, or SM-5 fuses need to be installed to meet
equired inte
upting capability. In areas near 12kV substations, the inte
upting rating of T-link
fuses may be exceeded. In these situations, SMU-20 fuses need to be installed to meet required
inte
upting capability.
Fuse total clear curve should detect minimum end-of-line bolted faults with a margin of 1.5 or
greater. A fault detection margin of 2.0 or greater is prefe
ed.
Maximum normal and contingency loads should not exceed the fuse manufacturer’s published
continuous and 8 hour ratings respectively.
Date DISTRIBUTION FEEDER PROTECTION
Standard Revision
PS-50 4
12/12
Electrical Distribution Design Standard
Sheet
13 of 64
Coordination requirements are as follows:
Fuse-Fuse Coordination
The upstream fuse must not be damaged by a fault beyond the downstream fuse. The total
clearing time of the downstream fuse should be less than 75% of the upstream fuse minimum
melt time. Fuse-fuse coordination is shown in Tables 4-1 through 4-4. In general, for fuses of
the same curve shape, fuses in series should be offset by two sizes in order to coordinate.
Hydraulic Recloser-Fuse Coordination
The upstream recloser must not lock out for a fault beyond the downstream fuse. To ultimately
achieve lock out coordination using hydraulic reclosers, a time margin of at least 0.1 second
etween the total clearing time of the fuse and the recloser delayed time is required. Also, the
ecloser can be used to clear temporary faults downstream of the fuse, without damaging the
fuse, by operation on its fast curve. To achieve fuse savings, a time margin of 0.1 second
etween the recloser fast curve and the fuse minimum melt curve is required to prevent
damaging the fuse. As such, recloser-fuse combinations that meet these two constraints over the
applicable fault cu
ent range are prefe
ed. However, recloser-fuse combinations that provide
lock out coordination are required. Recloser-fuse coordination is shown in Table 4-5.
Circuit Breake
Electronically Controlled Recloser-Fuse Coordination
The upstream circuit
eake
electronically controlled recloser must not lock out for a fault
downstream of the fuse. To ultimately achieve lock out coordination, a time margin of at least
0.1 second between the total clearing time of the fuse and the overcu
ent relay time is required.
The circuit
eake
electronically controlled recloser may be used to clear temporary faults
downstream of the fuse, without damaging the fuse, by operation of an instantaneous relay. To
achieve fuse savings, a time margin of 0.1 second between the instantaneous relay operating time
plus the
eaker clearing time and the fuse minimum melt curve is required to prevent damaging
the fuse. As such, circuit
eake
electronically controlled recloser-fuse combinations that meet
these two constraints over the applicable fault cu
ent range are prefe
ed. However, circuit
eake
electronically controlled recloser-fuse combinations that provide lock out coordination
are required.
Circuit
eaker-fuse coordination is discussed further in Section 6.0. The largest fuses that
coordinate with the standard
eaker settings are listed in Section 6.2. Standard electronically
controlled recloser-fuse coordination is shown in Table 4-5.Line Recloser Application
Date DISTRIBUTION FEEDER PROTECTION
Standard Revision
PS-50 4
12/12
Electrical Distribution Design Standard
Sheet
14 of 64
4.2 Line Recloser Application
Recloser voltage rating should meet or exceed the system operating voltage.
Recloser symmetrical inte
upting rating should exceed the maximum bolted fault level at the
point of application.
Recloser MTO must be less than the minimum end-of-line bolted faults with a margin of 1.5 or
greater. A margin of 2.0 or greater is prefe
ed. Hydraulic recloser MTO is typically twice its
ating. Hydraulic reclosers with an X designation (400X or 560X) have an MTO of 1.4 times its
ating. Relay / Microprocessor controlled recloser MTO is based on the trip settings of the phase
and ground elements.
Maximum normal and contingency loads should not exceed the recloser manufacturer’s
published continuous and 8 hour ratings respectively. Per Cooper Power Systems, hydraulic
ecloser emergency ratings are 125% of the trip coil rating.
Typically, hydraulic reclosers will have two fast and two delayed operations before locking out.
S&C Intellirupters are electronically controlled reclosers used for backbone protection. See
section 5.2 for more details.
S&C Tripsavers are small reclosers that fit universal cutout fuse mountings. Tripsavers are used
in place of tap fuses for fuse saving. See Section 5.2 for more details.
Coordination requirements are as follows:
Recloser-Fuse Coordination
See section 4.1.
Recloser-Sectionalizer Coordination
See section 4.3.
Recloser-Recloser Coordination
The upstream recloser must not lock out for a fault beyond the downstream recloser. To achieve
lock out coordination, a time margin of at least 0.2 second between the delayed curves of both
eclosers is required. Trip coordination may be achieved between electronically controlled
eclosers and hydraulic reclosers however; trip coordination will rarely be achieved between
hydraulic reclosers. The upstream reclosers may trip on their fast curves when the downstream
eclosers trip on their fast curves. If not, then the upstream reclosers may trip on their fast curves
when the downstream reclosers trip on their delayed curves. Recloser-recloser coordination is
shown in Table 4-6.
Date DISTRIBUTION FEEDER PROTECTION
Standard Revision
PS-50 4
12/12
Electrical Distribution Design Standard
Sheet
15 of 64
Circuit Breaker-Recloser Coordination
The upstream circuit
eaker must not lock out for a fault beyond the downstream recloser. To
achieve lock out coordination, a time margin of at least 0.3 second is required between recloser
delayed operation and the overcu
ent relay curve for microprocessor based relays with
instantaneous reset.
For circuit
eakers with electromechanical relays which have time delay reset, a time margin of
at least 0.1 second is required between the total time of all delayed operations of the hydraulic
ecloser and the overcu
ent relay curve of the circuit
eaker. Also, a time margin of at least 0.3
second is required between the delayed operations the electronically controlled recloser and the
overcu
ent relay curve of the circuit
eaker. To achieve trip coordination, the instantaneous
elay setting of the circuit
eaker must be at least 120% of the maximum bolted fault cu
ent at
the recloser. However, in order to provide fuse savings on the remainder of the circuit, the
instantaneous relay setting is not usually altered to achieve trip coordination.
Circuit
eaker-recloser coordination is discussed in Section 6.0. The largest reclosers that
coordinate with the standard
eaker settings are listed in Section 6.2.
Date DISTRIBUTION FEEDER PROTECTION
Standard Revision
PS-50 4
12/12
Electrical Distribution Design Standard
Sheet
18 of 64
4.4 Distribution Transformer Protection
Each phase of a transformer bank is protected by a fuse.
Fuse voltage rating should meet or exceed the system operating voltage.
Fuse symmetrical inte
upting rating should exceed the maximum bolted fault level at the point
of application.
Fuse total clear curve should detect transformer low-side bolted faults with a margin 1.5 or
greater and protect the transformer damage curve. For single-phase and three-phase wye-wye
transformers, low-side faults are reflected to the high-side via the turns ratio. For three-phase
delta-wye transformers, low-side phase-to-ground faults are reflected to the high-side via the
turns ratio x XXXXXXXXXXLow-side multi-phase faults are reflected to the high-side as the three-phase
fault level via the turns ratio.
Fuse total clear curve should plot below the transformer damage curve. Damage curves are
developed per ANSI C57.12 standard.
For a category I transformer (5-500kVA single or three-phase) the damage curve is 25 times full
load cu
ent at 2.0 seconds and 12.5 times full load cu
ent at 8.0 seconds (I2T = 1250).
For a category II transformer (501-1667kVA single-phase and 501-5000kVA three-phase) the
damage curve is 2.0 seconds at maximum low-side fault, and 4.0 seconds at 0.7 x maximum low-
side fault. For delta-wye transformers the damage curve must be shifted by 0.577 for phase-
ground faults. Maximum low-side faults are calculated assuming infinite source bus. Note the
category II damage curve includes a frequent fault
anch based on transformer impedance
which must be protected.
Fuse minimum melt curve should exceed transformer magnetizing inrush cu
ent and allow a
minimum 0.3 seconds coordination time with low-side protection. Conservative estimates of the
worst case magnetizing inrush cu
ents are 12 times the nameplate cu
ent rating for 0.1 second
and 25 times the nameplate cu
ent rating for 0.01 second.
Maximum normal and contingency loads should not exceed the fuse manufacturer’s published
continuous and 8 hour ratings respectively.
Distribution transformer loading and impedance data is shown in Table 4-7. This data was used
as the basis to determine the appropriate fuse size.
Date DISTRIBUTION FEEDER PROTECTION
Standard Revision
PS-50 4
12/12