J. LI ET AL.

726

substation, single power source to substation, then it can

be got the fault group which would influence the security

of power supply; 3) Defining the fault group by experi-

enced dispatchers and operation analysts via visual man-

machine interface;

The expected fault set formatted by 1) and 2) has in-

cl

requirements for

co

ally

ha

3.4. Risk Indices

risk indices appropriate for regional

:

de

upply security of important users and high

ris

in

3.5. Risk Level

an quantify the risk of system, but for

3.6. Risk-based Correction Strategy Set

op opera-

d Control for High-voltage Distract

G

ed on sensibility calculation, integrating planning

m

n Con-

tro

r distract grid, the operation mode is usually radial

op

4. Conclusions

to determine the possibility of com-

uded most accidents of high frequency and high risk. 3)

is only as a necessary complement, which can reduce the

manual workload and maintenance.

Online calculation software has high

mputing speed. In paper [6], the author combined fault

enumeration and probability sampling method, and im-

proved computing speed by parallel computing in the

foreground and background. This approach has two

shortcomings: first, it increased hardware cost; second, it

raised inaccuracy by adopting fault sampling mode. We

absorb results of existing “static security analysis” re-

search to analyze fault, which can satisfy computing

speed requirement. This fault analyzing method utilized

AC-DC hybrid algorithm, and has introduced parallel

computing technology based on multi-processor work-

station. The approach has been improved by combining

with node optimization, matrix inversion and node type

conversion, etc, which has greatly improved computing

speed. The correctness has been verified by the applica-

tion in regional-level scheduling, provincial scheduling

and city-level scheduling. For the test of 2000 nodes sys-

tem, it only needs 3s scanning whole grid lines, trans-

formers and units. The computing time would slightly

increase with the increase of limit violation number.

As important users and high risk customers gener

ve double power source, if not considering hot backup

source in fault analysis, the risk indices of loss of load

computed would deviate greatly with actual situation. So

when the main source of important users or high risk

customers break down, it should be analyzed after put-

ting into backup source.

It is presented three

grid in this paper according to formula(1): ①line over-

load risk; ②bus low-voltage risk; ③loss of load risk.

We compute risk indices ①,② by the formula, here

notes the limit violation of line power flow and bus

voltage; X denotes security upper limit or lower limit; the

superscript 2m is used to overcome the "shelter" de-

fect[4].

The power s

k customers is related to a range of social, political and

economic issues. The outage severity of these users de-

pends not only on the district grid’s own characteristic,

but also on the users’ property. We introduced an impor-

tance factor to classify these users, and because of lack-

ing outage time, we only compute loss of load risk indi-

ces, not outage cost evaluation indicators. The computing

formula of risk ③ is as, here: is the importance of the

jth load; denotes the reduction amount of the jth load

after failure I; is the load number of reduction.

We adopted real-time failure probability model denot-

g the probability. For outdoor components, the weather

condition value is set by dispatchers; for indoor compo-

nents, the weather condition value is constantly equal to

0.

The risk indices c

dispatchers, it is more expected that the risk indices can

directly show the system security condition. So we clas-

sified three risk grades according the risk value: security

level, alerting level and over standard level.

Distract grid is closed-loop design but open-lo

tion. When recovering, the distract high-voltage grid

(220 kV and above) and radial distribution grid lower

than 110 kV, different correction and control measures

should be adopted.

a) Correction an

rid

Bas

ethod and objective function selecting, then giving the

control target and control variable, the correction meas-

ure can be obtained for load and generation unit.

b) Distract Low-voltage Radial Grid Correctio

l

Fo

eration under close-loop. It is generally adopted ad-

justing operation mode as effective measure to ensure

continuous power supply and eliminate limit violation.

The correction strategy includes load balance, single

power source switch, multi-source load transfer, etc. In

extreme cases, it can be adjusted by removing load ac-

cording to load importance. After eliminating fault, sys-

tem recovery takes into account recovery path constraints

and risk indices constraints.

It is often difficult

ponent failure due to lack of statistical data. And the pos-

sibility of outdoor component failure has closely rela-

tionship with climatic conditions. For power dispatching,

it is originally difficult to get weather forecast parameters.

Even if it can be obtained the weather forecast parame-

ters, it has possibly an error. In this paper, based on util-

ity theory and probability theory, we have established the

three-dimensional model of failure probability by making

fully use of the dispatchers’ operation experience and

Copyright © 2013 SciRes. EPE