Bruce + West Bottling

The IESO Transmission System

• The transmission system is made up of a number of circuits all of which have unique capabilities and thermal limitations.

• Our generation dispatching tool is designed to recognize these limitations and dispatch resources appropriately in order to respect them.

• These limitations at times lead to an inability to utilize available generation due to a lack of paths out of a region – Bottled Energy

The IESO Transmission System

• These values are dynamic and can change every 5 minutes based on temperature, wind speed, day/night etc...

• Result of which are two schedules (constrained and unconstrained)

• As these limitations are automatically respected there is no formal operating instruction for how to manage these limits.

• In other words, no SCO exists for these sub-areas

Circuit Thermal Ratings

• The thermal capabilities of the circuits are provided to us from each circuit’s asset owner

• Revised thermal limits, in the form of a lookup table are provided to the IESO for each circuit every hour to reflect current real time conditions.

Bottling Estimates

•Bottled generation is normally calculated by zone whereby:

•Bottled Gen = Available Gen-Zonal Demand-Ability to leave Zone

•Zones are generally divided by transmission interfaces.

Bruce + West Transmission

WEST

BRUCE

SOUTH WEST

FABCW

BLIP

NBLI

P

MICH-ONT

INTERFACE

Interface Limits

•FABCW is the Flow Away from the Bruce Complex + Wind

•FABCW limit is dependent on a number of factors including actual flow on the BLIP interface.

•This limit is required to preserve plant stability in the area as well as to protect against voltage collapse post contingency.

•BLIP is the Buchanan Longwood Input.•BLIP flow 0 is generally limited to 3,000 MW and

Negative BLIP (NBLIP) generally varies between 500 to 1,500 MW.

•Both limits are based on voltage limitations

Interface Limits

• At times, the transmission capability internal to a zone may be more limiting than the interface limit.

• In these cases, the traditional methodology for measuring Bottling is not adequate

• This is the case in the West and thus the zone was divided into 4 sub-areas, each divided by a boundary.

• The traditional bottling equation is then applied to each individual sub-area.

```

NBLIP

The WEST

MICH-ONT

G

L

G````

L

G

L

G

L

≈ 500 - 1,500 MW

1. 3,058 MW – 4,045 MW

2. 3,010 MW – 3,981 MW

3. 2,218 MW – 2,836 MW

Boundary Thresholds

Each sub-area contains both generation and load.

Bottling In The West

• These four boundary thresholds are based on simulations done by the IESO.

• The simulation was designed to maximize generation.

• The boundary threshold values are the estimated maximum total generation that can be produced before a thermal limit of a circuit out of that sub-area begins to encroach on its limit.

• These boundary threshold values are used as estimates for modelling purposes only.

Bottling In The West

• Because these boundary are a result of thermal restrictions, each boundary has a different threshold for a number of temperature ranges.

• The threshold range is based on temperatures from -20°C to 35 °C and change by 5°C increments

Boundary Thresholds

Temperature (°C)

Boundary 1 (MW)

Boundary 2 (MW)

Boundary 3 (MW)

-20 4,045 3,981 2,836

-15 3,968 3,905 2,786

-10 3,885 3,824 2,737

-5 3,789 3,729 2,684

0 3,711 3,652 2,635

5 3,629 3,571 2,586

10 3,531 3,476 2,537

15 3,431 3,376 2,467

20 3,353 3,300 2,418

25 3,256 3,205 2,353

30 3,155 3,105 2,287

35 3,058 3,010 2,218

Looking Forward

• Transmission enhancements throughout the province

• The shutdown of coal fired generation

• Bottled numbers are expected to decrease

Thank You!Questions?