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Select the appropriate definition of Interchange:
a) Transmission arrangements for moving energy across Balancing Authorities
b) Transmission arrangements for moving energy between Transmission Operators
c) Energy transfers that cross Balancing Authorities
d) Energy transfers that cross Transmission Operators
c) Energy transfers that cross Balancing Authorities
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Continental North America is divided up into how many electrical interconnections?
- Three
- 1) Western Interconnection
- 2) Eastern Interconnection
- 3) ERCOT (Texas)
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Identify all the benefits to power systems being electrically interconnected:
a) Efficiency
b) Markets
c) Reliability
d) Large Disturbances
e) All of the above
- a) Efficiency
- b) Markets
- c) Reliability
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What is a Balancing Authority?
The responsible entity that integrates resource plans ahead of time, maintains load-interchange-generation balance within a Balancing Authority Area, and supports Interconnection frequency in real time.
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What is a Transmission Operator?
The entity responsible for the reliability of its "local" transmission system and that directs the operations of the transmission facilities.
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What is a Purchasing-Selling Entity?
The entity that purchases or sells, and takes title to, energy, capacity, and Interconnected Operations Services. PSEs may be affiliated or unaffiliated merchants, and they may or may not own generating facilities.
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True or False:
A Transmission Service provider is responsible for administering the transmission tariff and providing transmission services to Transmission Customers under applicable transmission service agreements.
True.
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BC Hydro is registered as which of the following? (Select all that apply).
a) Purchasing-Selling Entity
b) Balancing Authority
c) Transmission Operator
d) Transmission Service Provider
e) Interchange Coordinator
b) Balancing Authority
c) Transmission Operator
d) Transmission Service Provider
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What is the OATT?
Open Access Transmission Tariff.
The OATT sets out the terms and conditions by which BC Hydro conducts business with its customers.
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Why is BC Hydro designated as the Balancing Authority of the provincial electrical grid?
Because BCH is responsible for maintaining, operating and planning for the growth of BC's electric transmission system and supplies competitive services for generation dispatch and distribution operations.
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What is the NAESB?
North American Energy Standards Board.
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What is the purpose of the BCH Business Practices?
Provide policy and procedurees for doing business with BCH and include specific detail and/or clarification on the implementation of the OATT.
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What is our neighbouring BA to the East?
AESO - Alberta Electric System Operator.
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What is our neighbouring BA to the South?
BPA - Bonneville Power Administration.
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What is a Path? How many paths does BCH have with neighbouring BAs and what are they identified as?
A Path is an interconnection between BAs that is made up of transmission facilities that have been grouped together. From a scheduling point of view, paths are discussed at a transmission contract level. However, once the energy is actually flowing it will take the path of least resistance to get to its destination and this may not be on the path as contracted.
- BCH has two paths with neighbouring BAs:
- Path 1 connects BCH to AESO
- Path 3 connects BCH to BPA
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Which transmission facilities make up Path 1?
- - 500 kV Cranbrook to Langdon (5L94)
- - 138 kV Natal to Pocaterra (1L274)
- - 138 kv Natal to Coleman (1L275)
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Which transmission facilities make up Path 3?
- 500 kV Ingledow to Custer ties (5L51 and 5l52 - "West-side" ties)
- 230 kV Nelway to Boundary tie (2L112)
- 230 kV Waneta to Boundary tie (L71 - "East-side" tie, normally open)
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Define POR.
A POR (Point of Receipt) is a location that a Transmission Service Provider specifies on its transmission system where an Interchange Transaction enters or a Generator delivers its output. Essentially, the POR is the point where the energy will be "picked up."
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Describe the internal paths that BCH uses to move energy inside the province.
BCH has internal paths that are used solely for the transfer of energy across transmission facilities within the BCH BA.
One is the Interior > LM path, used for the transmission facilities that deliver power from the interior portions of BC to the Lower Mainland. Currently this path is separated out from the normal BC > US path because at times there is less transmission capacity than the BC > US path, making it a congestion point.
The other internal path is the BCHA > BCHA path, used for transmission services that do not leave the BCH BA but do cross various POR/PODs, including from BCH to FBC. It is also used for IPPs outside the LM that are moving energy to load within the interior portion of the BCH BA.
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What is a wheelthrough? On which paths do we have wheelthroughs?
A wheelthrough path is a contractual path for the flow of energy across various transmission facilities. In our case, the wheelthrough paths from one border of our BA to the other.
We have wheelthroughs on these two paths:
The energy never actually "synchs" within BC as it travels from AB to US or vice versa, so the POR and POD are the physical borders between our system and the US and our system and AB.
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What is TTC?
TTC is the maximum amount of actual power that can be transferred over direct or parallel transmission elements comprising:
- - an interconnection from one Transmission Operator area to another TO area
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- - a transfer path within a TO area
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True or False: BCH follows the Rated System Path Methodology for the development of its TTCs from MOD-029.
True.
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What is the maximum TTC for Path 1 in each direction?
East to West: 1000 MW
West to East: 1200 MW
(As of 2011)
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What is the maximum TTC for Path 3 in each direction?
North to South: up to 3150 MW on all ties
South to North: up to 2000 MW on all ties
(As of 2011)
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Define Incremental Transfer Capability. Where are Incremental TTCs found for both Path 1 and Path 3 from a BCH perspective?
Incremental Transfer Capabilities are values that are incorporated from system studies during times when the system is not normal and the path transfer capability is not the maximum.
- ITTCs for Path 1 are in SOO 7T-17
- ITTCs for Path 3 are in SOO 7T-18
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True or False: the TTC that is set on an hour by hour basis is used as the foundation for the purchase of transmission service.
True.
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True of False: TTCs are entered by the TC on the Effective TTC display in MODS.
True.
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Define TRMu.
TRMu (Transmission Reliability Margin Unreleased) is an amount of transmission set aside to account for uncertainties in load forecasting and other errors. TRMu is deducted from the TTC limit and is used in calculating the SL.
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Define TRM.
TRM (Transmission Reliability Margin) is an amount of transmission set aside between teh TTC limit and the ATC Firm Limit. Since TTC is always changing on an hour-by-hour basis, TRM is a calculated value which is "greyed out" and not enterable on the Effective TTC display.
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What is the definition of ATC?
ATC (Available Transfer Capability) is a measure of the transfer capability remaining in the physical transmission network for further commercial activity over and above already committed uses. It is defined as TTC less existing transmission commitments (including retail customer service), less a Capacity Benefit Margin, less a Transmission Reliability Margin.
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What is the Scheduling Limit?
The Scheduling Limit (SL) is the maximum amount of Net Scheduled interchange that can exist across a path. The SL is a calculated value based on the TTC, the TRMu and Counter Flow Energy Schedules.
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What are Counterflow Energy Schedules and how do they impact the Scheduling Limit?
Counterflow Eenrgy Schedules (CES) are energy schedules that are flowing in the opposite direction of the TTC direction. They impact the SL by effectively increasing it by their CES value.
For example, if the SL from BC to AB was 415 MW (TTC = 480MW - TRMu = 65MW = 415MW) and 50MW of counterflow energy were set to flow from AB to BC in the same hour, the SL would increase to 465MW.
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What is the definition of OTC? Is it synonymous with TTC from a BCH perspective?
OTC (Operating Transfer Capability) is defined as the maximum path rating which may be impacted temporarily due to short duration outages of transmission elements. Yes, TTC is synonymous with OTC from a BCH perspective. OTC is a term no longer used by NERC, but it is still used in WECC Regional Standards.
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What is the calculation for SL? Does this calculation ensure the net schedules for a path stay below the OTC/TTC limit?
SL = TTC - TRMu + Counterflow energy schedules
Yes, this calculation should ensure that the ent schedules for a path stay below the OTC/TTC limit for a given hour, unless a contingency occurs in that hour.
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Where is OTC monitored?
OTC is monitored by EMS. The system is capable of determining the proper OTC monitoring limit and time-based requirement based on information from the following:
- - MODS
- - TSA-PM
- - Manual Entry
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Do TTC limits from MODS get automatically entered in the OTC Monitoring display in AREVA?
Yes. When the TC manually enters a TTC value in the Effective TTC Summary in MODS, it gets pushed over to AREVa in the OTC Monitoring Display.
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Can manually entered values in the OTC Monitoring display override the TTC entered from MODS for OTC monitoring?
Yes. When a value is entered into the "Manual Entry" field in the OTC Monitor Summary, it will override the TTC value in MODS.
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What happens if the actual schedule exceeds the TTC limit in the OTC Monitoring display?
If the actual schedule exceeds the current hour TTC limit in the OTC Monitoring display, an OTC violation timer will start and alarms will be received by the TC and the GC. Actual flows must be reduced to within the OTC Limit in the allotted time frames for compliance.
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What is the maximum amount of time OTC can be violated for a stability constraint?
20 minutes.
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What is the maximum amount of time OTC can be violated for a thermal constraint?
30 minutes.
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