Contents - Index

Power System Toolbox

Version 1 of this toolbox was added to ATPDraw v5.9. This was extensively built on a recursive DFT algorithm for calculation of phasors.
It later became evident that this algorithm had some problems related to:
  • Memory allocation problems in MODELS for small time steps. One period of the signal must be remembered to calculate phasors.
  • 60 Hz system frequency gave accuracy problems as well as a delay cell allocation problem.

    To overcome the memory allocation problem downsampling had to be used. MODELS supports an easy way of doing this as the timestep can be declared locally for each model. With downsampling, the original DFT algorithm got substantially reduced accuracy and was enhanced by Radix2-8/16 FFT-routines. Models containing this routine requier SampleFreq input that should be multiples of 8*FREQ for the Radix2-8 routine and 16*FREQ for the Radix2-16 routine. Many of the Models have also an algorithm selection where Algorithm=1 gives a recursive DFT algorithm, while algorithm=0 gives the Radix2 algorithm. As with all Models make sure to specify unique UseAs names for Record and plotting.

    Most of the components in the toolbox are based on MODELS. The used must click on the input node to define the type of input (current, voltage, model etc). In the case when such models are connected together the Model producing an output to be used as input must be declared first in the ATP file. This is done by giving an Order number less than the Model receiving the output, and usage of 'Sorting by Order'.

    The toolbox in ATPDraw version 6.1 consists of

    Component Purpose
    BUS Three phase special component with #Bay control, Voltage, PQ load and surge arrester.
    LINE3 Three phase special component with symmetrical component RLC input for selectable lumped or distributed parameters. Optional CB, CT and flexible fault location. Color coding according to View|Options/PS Colors. The component behaves like the standard connection and follows the Edit|Rubber band flexibility.
    LOADPQ A voltage dependent PQ load model. P=PN*(V(VN)**Np, Q=QN*(V/VN)**Nq. This component is really a Group stored in the /GRP folder. It contains some advanced initialization features (ABC2PHRI)
    RMS Calculate RMS values of a 3-phase signal by integration.
    ABC2PHR Calculation of 3-phase phasors with a given fixed frequency. Output is real and imaginary value of the phasers. Can be used together with a WRITEPHASOR component for plotting.
    ABC2PHRI Calculation of 3-phase phasors with a given fixed frequency. Initialize the phasors be utilizing the imiginary part of ATP's steady-state analysis.
    ABC2PHRF Calculation of 3-phase phasors with a variable frequency calculated by a PLL component. 
    ABC2PHRH Calculation of 3-phase phasors for a fundamental frequency and a specified harmonic. Typically for transformer differential relays with 2/5 harmonic restraint.
    ABC2SEQ Calculate of sequence component phasors for a given fixed frequency.
    WRITEPHR Writes the phasor values to the LIS file at a specific time, reads it back in after the simulation and has a View module for plotting.
    PLLDQ Calculate the frequency of the signal. Has also internal algorithms for estimation of the amplitude.
    HARMONICS Calculation of multiple harmonics using the original DFT algorithm. SampleFreq<1/deltaT reduces accuracy.
    UI2PQ Calculate the active and reactive power for the three phases. The Current input must be connected to a switch and watch out if several switches are connected to the same node as ATP will give you the current through the switch declared first in the ATP file. User the Order or Current probe middel point to control this.
    UI2PQ3 Calculate the total 3-phase active and reactive power. Version 6.1 offers also a third ab algorithm to calculate the power.
    WMETER Calulates the instantaneous and average 3-phase active power from an integral formulation (not FFT).
    UI2RXL Calculates the resistance and reactance of the (Ua-Ub)/(Ia-Ib) phasors to be used with distance relays W1RELAY21 (phase-faults)
    UI2RX Calculates the resistance and reactance of the Ua/Ia phasors.
    UI2RXE Calculates the resistance and reactance of the Ua/(Ia+k0*I0) phasors to be used with distance relays W1RELAY21 (earth faults)
    W1RELAY51 Constant time-delay over-current relay. Requires RMS value input. Output Trip, and Info. Has a Block input.
    W1RELAY51I Inverse time over-current relay. Requires RMS value input. Output Trip, and Info. Has a Block input.
    W1RELAY67N Directional zero-sequence over-current relay.
    W1RELAY21P Distance relay with polygon sone shapes (3 zones). Requires RX input either from UI2RXL (phase faults) or UI2RXE (earth faults). Output Trip, and Info. Has a Block input.
    W1RELAY21C Distance relay with circular sone shapes (3 zones). Requires RX input either from UI2RXL (phase faults) or UI2RXE (earth faults). Output Trip, and Info. Has a Block input.
    W1RELAY87T Transformer differential relay. Requires current phasor input and its restraint harmonics (typically 2 or 5). Output Trip, and Info. Has a Block input.
    W1RELAY87L Line differential relay. Requires current phasor input and its restraint harmonics (typically 2 or 5). Output Trip, and Info. Has a Block input.
    W1RELAY27 Under-voltage relays with two steps. Output Trip, and Info. Has a Block input.
    W1RELAY59 Over-voltage relays with two steps. Output Trip, and Info. Has a Block input.
    W1RELAY81 Frequency relay over/under with two steps each. Output Trip, and Info. Has a Block input.
    TACS RMS, FREQ, DQ0, ABG (abg). Three-phase TACS component with circuit variable coupling. Only one such component is possible at each node.