Smart Grid Where We Are Today?

Transcription

1 1 Smart Grid Where We Are Today? Meliha B. Selak, P. Eng. IEEE PES DLP Lecturer 2014 IEEE ISGT Asia, Kuala Lumpur 22 nd May 2014

2 2 Generation Transmission Distribution Load

3 Power System Transmission 3

4 Power Transfer P1 Vs Pt Vr 0 P2 L1 For power balance P1+P2=L1+L2 L2 For power flow Pt = P1 L1 = L2 P2 Vs x Vr x Sin(q) XL

5 Transmission Line Model Electrical Behavior of Transmission Line [dv/dx]=[z][i] [di/dx] = jω[c][v] Series impedance matrix [Z] Z Z Z ii ik R( ) j L( ) R c ii j L j L ik ii

6 jb a P r h L i i o ii 2 ln 2 jd c d D L ik ik o ik ' ln 2 j o o P Transmission Line Inductance

7 c R ii f h r d i i D ik ' ik a.c. resistance of conductor i, 2f, angular frequency, frequency in Hz, average height above ground of conductor i, radius of conductor i, direct distance between conductors i and k, distance between conductor i and image Formula Quantities Z Z o o ii ik at complex depth of conductor k, earth resistivity, earth permeability. R c ii j ( a jb ) ( R j ( c jd ) d jc c ii b) R ik ja L ik. R ii jl ii,

8 8 Building Complex Power Systems Power system is very complex and is built to satisfy increasing demand of electrical power supply The trend in electric power production is toward an interconnected network of transmission lines linking generators and load into large integrated system

9 9 Power System Operation Operation of an electrical power systems involves continues electromechanical and electromagnetic distribution of energy. During normal operation the system behavior is presented by voltage and current pasors in frequency domain. During system disturbances the circuit components have higher stress, resulting in excessive currents or voltage variations that cause power system transients.

10 Power System Studies Steady State Study Dynamic State Simulation Transient Simulation

11 11 Simulations Outputs Steady State Short Circuit Fault Level Equipment Selection (isolation level) Reference for Protection Settings Dynamic State Simulation Speed of the fault clearing time Transients Simulation Tripping Priority regarding to: Overvoltage's conditions and Power Quality (harmonics)

12 12 Power System Disturbances and Faults Inadequate supply equipment Result of inadequate planning or unexpected rapid load demand Exceeding supply capability results in load losses Many blackouts caused by operating systems too close to stability limits

13 13 Protection Duties Protection system or relay must detect the fault and signal circuit breaker to isolate the fault reliably and as fast as possible.

14 Relaying Fundamentals 14

15 Example reaches and time coordination 15

16 16 Stepped Distance Note: NOT communications assisted, but good background for other schemes Z2a Z1a Z1b Z2b

17 17 Adding large generating units With adding large generating units of high capacity to the power grid endangers the normal operation of power system and might lead to outages and system collapse. The convention power system protection schemes, designed to detect the fault and signal circuit breaker to isolate the fault reliably and as fast as possible, but cannot prevent from the system collapse.

18 18 Telecommunications infrastructure Nowadays, the modernized networks and telecommunications infrastructure together with Intelligent Electronic Devices (IED), and allow optimizing the existing electrical power system operation.

19 19 Intelligent Electronic Devices (IED) IEDs which are used now widely for Power System Protection allow us an implementation of almost all the functionalities needed to protect and control the power system components more efficiently: Fundamental protections (Over Current, Over Voltage, Over Frequency, Distance, Differential Protections) Breaker Failure protection (BFPN) Autoreclose (AR) Automatic switching of protection settings Overload protection Wide area special protection schemes (SPS) or remedial action scheme (RAS) Synchronized Phasor Measurement

20 20 Wide area special protection schemes Wide area special protection schemes (SPS) or remedial action scheme (RAS) are designed to detect the system conditions that can cause instability overload voltage collapse Prevent propagation of disturbances for severe system emergencies caused by un planned operating conditions Last line of defense to improve system security and prevent disturbance propagation Could help better utilize system margins Stabilize System for Equipment Outages, N 2 or beyond Initiate pre planned separation of the power system Prevent overloading of the lines Arrest voltage decline

21 21 Synchronized Phasor Measurement Two key elements of synchronized phasor measurement are data that are provided how that data are referenced Synchronized phasor measurement system requires a high-precision timing reference (Global Positioning Satellite Clock system) to synchronize all devises across a system-now available from monitors called phasor measurement units (PMUs) Voltage waveforms from remote measurement units are compared on realtime basis. This capability is used to: evaluate system conditions compered them to the system model facilitates analysis in system-wide disturbances system operation control generation dispatch

22 22 Permissive Overreaching Transfer Trip Z2a Z1a Z1b Z2b Sending Permissive Trip = fault is in front of me Received Permissive Trip + local Zone 2 = local trip

23 23 Why communication assisted line protection? Speed, speed, speed Selectivity problem (ie: is the fault between the two ends of the line?) Adding communications allows cooperation between both line terminals, which improves speed by improving selectivity

24 24 Power Distribution System Distribution system is designed to serve radial load. (Power flows from higher voltage levels down to customers)

25 25 Distribution Protection Relay characteristics are plotted on a time current characteristic (TCC) diagram. Non directional protection is needed because of radial system configuration

26 Electrical Power System Today G Generation G Supply Transmission Traditional one-way supply system Bi-directional supply system G Distribution Loads Generation G Generation Transmission Distribution Loads Demand Generation Interconnections

27 27 Concerns related to the distribution system operation and planning With DG increases, Distribution Systems are becoming more like transmission system: double or multiple feed circuits having significant changes in operation will have to accommodate bi directional power flows safety of public and equipment as the network was not designed to accommodate larger numbers of DG protection system becomes more complex due to changes in system behavior and power flow under shortcircuit conditions

28 28 Need for directional protection F1 R1 faster than R2 F2 R2 faster than R1

29 29 Distribution Systems Today Today, the power distribution systems are designed to provide participating customers a new level of choice and control over their energy use through advanced technology, with the goals of empowering customers to: save energy increasing electric service reliability improving response to power outages.

30 30 Distribution Systems Today Advanced communications technologies Smart meters Devices for electrical system automation Energy management tools ALL provide the significant benefits for energy customers. The new global communications platforms support the future innovation: wide and local area networks telecommunications services voice services video conferencing