Title: Transmission Off-Take Allocation and Balancing Procedure

SYSTEM OPERATIONS

OPERATIONAL PROCEDURE No. 13

TITLE: TRANSMISSION OFF-TAKE ALLOCATION AND BALANCING PROCEDURE

Issue:1Date:May, 2010

Issue: 2Date: September, 2013

Approved by:

ED (SO)-Dipak Sarma

SYSTEM OPERATOR CHQ, ABUJA

Last Review Date: September 2013

Originator: ED SYSTEM OPERATIONS

SYSTEM OPERATIONS

OPERATIONAL PROCEDURE No. 13

Issue no. 2

TRANSMISSION OFF-TAKE ALLOCATION AND BALANCING PROCEDURE

Contents

1.BACKGROUND, PURPOSE AND SCOPE

1.1.INTRODUCTION & GENERAL ISSUES

1.1.1.Position of Imbalance Calculation

1.1.2.Disco to Disco Direct Flows

1.1.3.Power Station Imports

1.1.4.Process Fees

1.1.5.Interconnectors (IC) and Directly Connected Customers (DCC)

1.1.6.Transmission Constrained Flows

1.1.7.Transmission Loss Adjustment

1.2.PURPOSE

1.3.SCOPE

1.4.LEGAL LINKAGE

2.ISSUANCE, RESPONSIBILITY AND USE

2.1.ISSUANCE

2.2.RESPONSIBILITY

2.3.USERS

3.TECHNICAL

4.PROCEDURES

4.1.ASSUMPTIONS

4.2.MONTH AHEAD

4.3.DAILY OPERATIONAL PLANNING DUTIES

4.4.MONTH END

5.DEFINITIONS AND ACRONYMS

6.STATUS AND ASSOCIATED PROCEDURES

SYSTEM OPERATIONS

OPERATIONAL PROCEDURE No. 13

Issue no. 2

TRANSMISSION OFF-TAKE ALLOCATION AND BALANCING PROCEDURE

1. BACKGROUND, PURPOSE AND SCOPE

1.1. INTRODUCTION & GENERAL ISSUES

This procedure is required under the Transition Market Rules to allocate the output from generation between the parties taking delivery from the Transmission Grid system (distribution companies, directly connected customers and exports to other countries – called transmission off-take parties {TOPs}).

This current version of the procedure deals with the environment where there is insufficient generation to meet demand on an almost continuous basis. Once there is sufficient generation to meet demand for a significant proportion of time, this procedure should be revised.

The procedure has been created as an SO procedure, but it covers both SO and MO balancing actions for the following reasons:

a) The SO procedure already exists and is NERC approved hence the process for change just requires SO (plus MO) approval and submission to NERC on the basis of non-disapproval.

b) The vast majority of the actions under this procedure are the SO’s with the MO actions largely being covered directly in the Market Rules and existing Market Procedures.

1.1.1. Position of Imbalance Calculation

Imbalances can be calculated either:

1) At the power station delivery points; or

2) At the Disco off-take points.

Provided prices and volumes are adjusted for transmission losses these are equivalent.

In this draft of the procedure:

1) Contractual energy imbalances are at Disco boundaries

a) payments use contract prices adjusted upward for transmission losses;

2) Disco Fixed Cost Amounts are calculated at Disco boundaries; and

3) Disco daily off-takes are at disco boundaries.

1.1.1.1. Imbalance Interpretation

Imbalances can be positive or negative and when fully calculated will sum to zero. It is however easy to get confused as to which is positive and which is negative:

1) In OP13 it is decided that the party who is owed money, i.e. who has not taken sufficient energy is positive so his Under-Delivery Quantity is positive. Contrariwise if a party has a negative Under-Delivery Quantity (i.e. it has overtaken) then it owes money.

1.1.2. Disco to Disco Direct Flows

The current procedure does not cover direct flows from Disco to Disco and the SO does not see them. There are two general classes:

1. A direct flow at lower voltage from one Disco to another at lower voltage: Note that this should increase the distribution technical losses in the delivery network.
2. A single transmission substation feeding two (or more) Discos through one set of meters.

1.1.2.1. Solution

1. The MO is to submit the total flow for each Disco pair for the previous month to the SO. As this will not arrive until a few days into the month so for month end calculation, the previous month’s value should be used.

1. The SO is to assume that the daily flow for each pair is the historic monthly flow divided by days in the month.

1.1.3. Power Station Imports

When the whole power station is shut down for a whole month they can end up as importers. This is a low probability event with small flows. The MR does not currently cover this, hence it is essentially treated as transmission losses.

1.1.4. Process Fees

Process fees shall not be applicable because under the MR the costs are already embedded in the MO and SO budgets.

1.1.5. Interconnectors (IC) and Directly Connected Customers (DCC)

The current OP13 treats these as an extension of transmission losses, which is appropriate pre-TEM. The current generally assumed position on these is:

1) DCC will go to the surrounding Disco hence the Disco will “own the meters” and the values will be incorporated in their balance.

2) Similarly IC will purchase from NBET:

a) However NBET does not have any electricity left as all their purchases from Gencos are sold to Discos in Vesting Contracts which share the generation out on a percentage basis, totalling 100%;

b) This would mean that NBET has no purchase contracts to set off these IC flows;

c) Hence they will pay for them through imbalances;

d) While the IC case is workable currently this should be reset so that NBET has a percentage of the next set of generation PPAs that is not passed on to Discos.

1.1.6. Transmission Constrained Flows

The Transmission System is constrained in particular: some Discos (far from generation) will be delivered less than their contractual percentage; whereas others (close to generation) will be delivered more than their contractual percentage. The issue is:

1) Where there is more than one Disco behind a constraint how will the shortfall excess be shared?

a) The fairest choice is: allocation on a ratio of contract percentages.

2) On a monthly basis Discos will be told their total imbalance:

a) This is an SO number from the rolling daily values (this is from operational metering so for indication only); and

b) The MO number from commercial meters which will go into the charge calculation.

3) On a daily basis the Disco will be told:

a) Its expected off-take for the following day this will be its contractual rights adjusted for previous Under-Delivery Quantity.

i) For Discos that are constrained down this amount will be limited by the constraint:

(1) which will of course increase the Under-Delivery Quantity the following day.

ii) For Discos behind constraints the expected off-take will be increased in accordance with the excess generation available:

(1) the next day Under-Delivery Quantity will hence be a more negative number.

b) Its total Under-Delivery Quantity at the previous midnight

c) Its expected total Under-Delivery Quantity at midnight end of next day.

1.1.7. Transmission Loss Adjustment

The SO procedure adjusts the Discos’ imbalances to the Power Station contract points. This fits with applying the average generation price.

For treatment of Disco fixed costs imbalance at Discos’ boundaries is probably correct. A clear and consistent approach is needed for the two cost factors.

Clarification of the MO settlement approach is needed as daily approach needs to match it.

1.2. PURPOSE

The purpose of this procedure is to ensure the allocation of generation output to Transmission Off-take Parties (TOPs) according to their contracts under the Transitional Stage Market Rules.

1.3. SCOPE

This procedure describes the process whereby the SO shall organise Disco off-takes in line with contracts and MO shall bill them and covers:

1) Required data inputs;

2) The System Operator (SO) is responsible for operating the Transmission Grid System in such a manner that TOPs receive their appropriate proportion of generation in accordance with their power purchase contracts (see Definitions). This operational procedure covers:

a) The issuing by the Market Operator (MO) of the contractual generation allocation requirements to the SO;

b) The SO’s practical operation to and updating of these allocations on a day-by-day basis;

c) Information to TOPs on what they should expect to receive;

d) Meter-flow information to the MO on actual allocation flows;

e) MO calculation of imbalance payments for fixed costs and energy.

1.4. LEGAL LINKAGE

The legal power is through Grid Code and Market Rules.

This requirement is given in the Multi-Year Tariff Order for Discos clause 5.7.

Amendment 7 to the Market Rules includes the calculation of the various quantities required under MYTO Disco clause 5.7.

This draft of the procedure is written in accordance with the MR draft for amendments 1 to 7 and will apply on their approval by the commission.

2. ISSUANCE, RESPONSIBILITY AND USE

2.1. ISSUANCE

This procedure shall be issued to all Users of the system, Participants in the market and system operators.

2.2. RESPONSIBILITY

The ED SO is responsible for reviewing, revising and reissuing this procedure. It shall be reviewed whenever the reference in clause 1.4 or the procedures listed in clause 8 are amended.

2.3. USERS

1) The General manager (S/O) National Control Centre is responsible for the operation of this procedure.

2) The MO shall appoint a manager to be responsible for MO duties under this procedure.

3) NBET shall appoint a manager to be responsible for NBET duties under this procedure.

4) Each Generator shall appoint a manager responsible for generator duties under this procedure.

3. TECHNICAL

None

4. PROCEDURES

4.1. ASSUMPTIONS

This draft procedure assumes:

1) Demand is not met on a regular basis hence the SO dictates flows to Discos to match their contractual rights.

2) Contract volumes assign a percentage of the generators output to a disco. It is also assumed that 100% of the output from each generator is contracted.

3) Contract percentages will apply on a monthly basis – hence accounted on this basis. It is expected that contract percentages will be the same for each month of the year {although this is not a necessity for this procedure to work}.

4.2. MONTH AHEAD

4.3. DAILY OPERATIONAL PLANNING DUTIES

• Inform shift staff of the target daily contractual output for each disco.
• Inform Discos of their target daily contractual off-take.
• Inform Discos of their rolling undertake for D-1
• Inform Discos of their expected rolling undertake for the end of D+1

4.4. MONTH END

• Using midnight month end readings calculate the monthly rolling undertake for each disco:

• To inform MO of the results of the above calculation.

• To inform the MO of:

5. DEFINITIONS AND ACRONYMS

Terms not listed here are defined in the Grid Code or the Market Rules.

Transmission Off-take Party (TOP): an entity taking power directly from the transmission system being a Distribution Company, Interconnector or Directly Connected Customer.

Delivered Generation: is the generation output reduced by transmission losses.

Contract: means a Vesting Contract.

Output Percentage Matrix: is the matrix derived from the contracts, sized as number of generators by number of discos, of the percentage of each generator’s output that goes to each disco.

Contractual Undertake or Undertake: the disco’s contractual right minus their actual off take. A positive number means that they are owed electrical energy by the system/market and a negative one means that they owe electrical energy to the system/market.

6. STATUS AND ASSOCIATED PROCEDURES

Status: Draft V2

As an Operating Procedure this procedure derives its legal power from the Grid Code, Market Rules and MYTO II distribution order.

The following procedures interact with this procedure.

Any changes to the above policy references will mean that the procedure must be reviewed and if necessary updated.

Annexes

The following proformas should be used where specified.

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