Download Wkshp_WECC-0100 LMTF Update_030816

Project WECC-0100 Update
Load Modeling Task Force
March 2016
Chuck Matthews
R1.1 Steady State Voltage
• Applicability – All applicable BES buses.
• Criterion:
– At all applicable BES buses
– 95% to 105% of nominal for P0 event,
– 90 to 110% of nominal for P1-P7 events
• Discussion
– Steady state voltage range for P0 event originates in ANSI C84.1
standard. No difference for 500 kV for simplification.
– Wider range for P1-P7 events to allow for contingencies. Voltage
regulators keep acceptable voltage to loads.
– Discussed definition of nominal. In this case TP/PC can define
nominal in their individual criterion if they need to for defining
voltage limits for their system (e.g. 525 kV).
R1.2 Post-Contingency Voltage Deviation
• Applicability - At each applicable BES bus serving load.
• Criterion:
– Post-Contingency steady-state voltage deviation at each
applicable BES bus serving load (having no intermediate
connection) shall not exceed 8% for P1 events
• Discussion
– The 8% for P1 events is based on some entities indicating a state
regulatory need, and some entities allowing 8% voltage deviation
for shunt reactive power device switching after an outage.
– For P2-P7 events it was concluded by the SDT it would be
acceptable to not have voltage deviation criteria that is more
stringent than steady state voltage criteria in requirement R1.1.
R1.3-1.6 Transient Voltage Performance
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Applicability - At each applicable BES bus serving load
Applies to P1-P7 events
R1.3 – Voltage recovery following fault.
R1.4 – Voltage dip following voltage recovery.
R1.5 – Same performance as R1.4 for contingencies
without a fault, P2.1.
• R1.6 – Oscillations required to show positive damping
within 30 seconds.
R1.3-1.4 Transient Voltage Response Criteria
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General philosophy of Criteria has changed from no loss of load to
maintaining integrity of the BES.
Criteria developed to accomplish three goals:
– Account for FIDVR
– Consider impact of more explicit load modeling
– Minimize loss of load that is non-consequential
R1.3 – Voltage recovery to 80% of pre-contingency voltage within 20
seconds
– Consideration for FIDVR events based on experience and industry
comments.
– Recognizes load loss initiated during fault can’t be prevented
R1.4 – With a fault, following recovery above 80%,Vdip below 70% for 30~,
below 80% for 2 seconds.
– Guidance from IEEE 1668 Trial Use Recommended Practice for Voltage
Sag and Short Interruption Testing for End Use Equipment. Type I and
II tests seems reasonable since majority of transmission faults are non
3-phase.
– Helps minimize load loss for subsequent swings.
– Also within ranges specified in IEEE 1547 Interconnecting Distributed
Resources
Impacts to Other Systems
• WR2. – If an entity uses more stringent Criteria than
WR1 shall apply that Criteria only to their own system.
• WR3 – If an entity uses less stringent Criteria than WR1
shall allow others to have same impact to that part of
system.
• These requirements carry over from the previous Criteria
requirement WR2 which allowed systems to apply
different requirements than Table W-1.
• Retains the philosophy of “allowable effects on other
systems”.
WR4. Cascading and Uncontrolled Islanding
• Threshold Criteria to identify potential for Cascading or
uncontrolled islanding.
• Criterion:
– Post contingency analysis results in steady-state facility loading
either exceeding 125% or the known trip setting.
– Transient stability voltage response R1.3, voltage recovery
longer than 20 seconds.
– When unrestrained successive load loss or generation loss
occurs.
• Discussion
– Since Cascading or uncontrolled islanding would manifest itself
differently in different parts of the system, the SDT developed a
threshold criteria where further investigation would be warranted.
– Regarding unrestrained successive load or generation loss, it is
anticipated this would be an iterative powerflow simulation
process as determined by the entity.
WR5 Voltage Stability
• Positive reactive power margin for the following:
– For transfer paths 105% or 102.5% of path flow for P0-P1 or P2P7 events respectively.
– For load areas 105% or 102.5% of forecasted peak load for P0P1 or P2-P7 events respectively.
• Discussions
– No technical justification to changing existing real power margins
used in previous Criteria.
– Concerns about specifying a particular methodology rather than a
Criteria.
– Path or load area assumed voltage stable by at least
demonstrating the margins specified. Discussion this is a criteria
for transmission Planning over the Planning Horizon, not a
methodology to find system voltage stability limits beyond what
the system is planned for.
WR6 Make Criteria Available
• Entity that uses study criteria different from criteria in
WR1 shall make their criteria available upon request
within 30 days.
Frequency Dip Criteria
• Frequency dip criteria is not included in this Criteria. A
frequency dip criteria was included in Table W1 which
was retired.
• There is no good technical justification for frequency dip
impact to load.
• Under frequency concern is to protect generators. UFLS
designed in coordinated fashion based on frequency
excursion to prevent excessive gen loss, not based on
frequency dip as defined by previous criteria.
• PRC-006 Automatic UF Load Shedding defines
requirements for PC’s developing UFLS Programs.
WECC ONF Requirements.
• Generator frequency capability requirements defined in
NERC PRC-024
Questions?