load flow studies.docx

7/27/2019 Load Flow Studies.docx

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Load Flow Studies

1. IntroductionThe load flow study reveals the steady state performance of the power system. Through the study

potential unacceptable voltage conditions and overloading of transmission network elements can be

identified.

2. Inputs for the StudyDemand in each grid substation can be obtained from National Power and Energy Demand Forecast,

published by CEB. The generation dispatch has to be worked out with reference to the Long Term

Generation Plan, also published by the CEB. NCRE Dispatch can be worked out based on the trial

scenario mentioned in the chapter 13.

The studies have to be done considering power system model with current and future

developments. Long Term Transmission Expansion Plan contains the data relevant to the

transmission system development and Long Term Generation Plan Specifies the expansion of

generation capacity. Specifically the steady state impact of two key proposals that would

significantly change the economic absorption capability of intermittent sources in Sri Lanka:

proposed India-Sri Lanka grid interconnection and the prospects of developing pumped storage

capacity have to be considered.

3. OutputsIdentification of steady state constraining factors when NCRE is integrated according to the each

scenario can be done.

Potential Technical Constraints

Unacceptable voltage conditions

Overloading of transmission Network Equipment

Depending on the technical limitations defining the capacity of each key renewable energy resource

that can safely absorb to the existing national grid can be found.

Proposing necessary adjustments to the grid in order to meet the identified constrains has to be

done in such a way that the power is delivered within the operating limits of the equipment in a

continuous manner without any wide spread failures. This will be an iterative process.

These capacities can be further evaluated over economical and any physical limitations in specific

geographical area where potential has been indicated in studies/scenarios proposed by the Master

Plan team.


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4. Criteria to be fallowed Voltage criteria

The voltage criterion defines the permitted voltage deviation at any live bus bar of the network

under normal operating conditions as given in table

: Allowable voltage variations

Bus bar voltage Allowable voltage variation (%)

Normal

operating

condition

Single

contingency

condition

220 kV 5% -10% to +5%

132kV 10% 10%

33kV - ???????????????

Thermal criteria

The design thermal criterion limits the loading of any transmission network element, in order to

avoid overheating due to overload. The loading of elements should not exceed their rated thermal

loading values for steady state conditions.

Security criteria

The performance of the transmission system under contingency situation is taken into consideration

in the security criteria. The adopted contingency level for the planning purposes is N-1, i.e. outage of

any one element of the transmission system at a time.

5. System AnalysisLoad flow studies should be performed on the model considering

1. Normal operation conditions

2. N-1 contingency conditions

3. Two generation scenarios

a. Hydro Maximum

b. Thermal Maximum

4. Three Loading Conditions

a. Day Peak (11.00 h)

b. Night Peak (19.30 h)

c. Off Peak (03,00 h)

Above 3 and 4 can be summarized in a table as bellow.


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Scenario LoadGeneration

Thermal Hydro

TMNP Night Peak Max Balance

TMDP Day Peak Max BalanceHMNP Night Peak Balance Max

HMDP Day Peak Balance Max

OP Off Peak Partial Partial

5. Five NCRE generation scenarios

These NCRE scenarios are explained in detail in chapter 13.

Description

Abbreviation

used

Energy Share

of NCRE-based

in this papergeneration inthe grid by2032

Very aggressive, wind dominant VAWD 30%

Aggressive, wind and biomass dominant AWBD 25%

Aggressive with solar, wind and biomass ASWB 25%

Aggressive, mixed scenario AMIX 20%

Early Solar, Aggressive wind and biomass ESWB 25%

6. Three loading conditions

a. Working Day (WD)

b. Week End Holiday (WE)

c. Public holiday (HD)

All together there are 75 scenarios to be considered.

TMNP TMDP HMNP HMDP OP

WD WE HD WD WE HD WD WE HD WD WE HD WD WE HDVAWD 1 6 11 16 21 26 31 36 41 46 51 56 61 66 71

AWBD 2 7 12 17 22 27 32 37 42 47 52 57 62 67 72

ASWB 3 8 13 18 23 28 33 38 43 48 53 58 63 68 73

AMIX 4 9 14 19 24 29 34 39 44 49 54 59 64 69 74

ESWB 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75

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