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# Power system tools

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# Power system tools

 The Power System Toolbox consists of 3-phase components for power system studies (short circuit and fault analysis and relay protection). Key elements are the LINE3 component that are drawn and edited like Connections and the various phasor calculators based on MODELS.

Fundamental components

These are the building blocks in power system studies with easy fault application. Combine this with the standard voltage and current probes with steady-state output.

 Selection Object name Icon ATP card Description Bus BUS3 BRANCH Multi-node (Bays) connection point with optional load and arrester. Line LINE3 BRANCH LINEPI3S or LINEZT_3 component with faults, CB and CT. Edited like Connections. Load PQ LOADPQ MODELS RLC+SRC Voltage dependent load model. Group with MODELS controlled source based on phasor calculation Ctrl CB CTRLCB MODELS SWITCH 3-phase TACS switch, opens at MODELS controlled zero crossing

Basic MODELS calculators

These calculators takes in 3-phase current or voltage chosen in the input node (left) dialog box.

 Selection Object name Icon ATP card Description RMS ABC2RMS MODELS Outputs RMS value of all 3-phase inputs Phasors +Basic ABC2PHR MODELS Outputs phasors (re, im) for all 3-phase inputs. DFT recursive or FFT methods with down sampling. Phasors +Initialized ABC2PHRI MODELS Same as ABC2PHR but with steady-state initialization at t=0 Phasors +Freq. variant ABC2PHRF MODELS Same as ABC2PHR but with frequency as input (from PLL) Phasors +1+h ABC2PHRH2 MODELS Calculate phasors (re, im) in fundamental frequency and one extra harmonic. Phasors +Sequence 012 ABC2SEQ MODELS Calculate phasors and convert it to sequence 012 output (re, im). Phasors +Write/Plot WRITEPHASOR MODELS Takes in phasors (re, im) to View this at specific instance in time Filters +Low pass BLPFILT MODELS 0-3 order Butterworth low pass filter with gain adjustment Filters +High pass BHPFILT MODELS 0-3 order Butterworth high pass filter with gain adjustment PLL PLLDQ MODELS Calculation of frequency based of park transform of 3-phase inputs Harmonics HARMONICS MODELS Calculation of 1-26 harmonics based on DFT recursive alg. Old.

Power and RX calculators

These calculators require input of 3-phase currents and voltages (top-left node is voltage, bottom-left node is current). Normally the two input nodes can simply be connected and further to a unique 3-phase switch node, as shown in Fig. 4.86 . Note that currents can only be obtained from switches and ATP will give you the current in the first switch connected to the node you specify. To make sure you get the correct current in the case of several switches connected to the same bus, you should connect to a node not shared by any other switch with a different current. The current probe with Add current node adds two measuring switches in series behind the scene and gives you access to the unique middle point.

 Selection Object name Icon ATP card Description PQ +PQ 3*1 UI2PQ MODELS Calculate active and reactive power per phase for 3-phase volt and curr. PQ +PQ 3-phase UI2PQ3 MODELS Calculate active and reactive 3-phase power. DFT+FFT+DQ alg. PQ +Watt meter WMETER MODELS Calculate average active power by integral method. No downsampl. RX + (Ua-Ub)/(Ia-Ib) UI2RXL MODELS Calculation of positive sequence impedance (R, X) for phase-to-phase faults. RX + (Ua-Ub)/(Ia-Ib) UI2RXE MODELS Calculation of positive sequence impedance (R, X) for phase-to-ground faults. RX +Ua/Ia UI2RX MODELS Calculates the impedance seen in each phase

Protective relays

These relays should be connected to RMS (over current, and under/over voltage), Phasor calculators (differential), and RX calculators (distance). The directional over-current relay has its own zero sequence phasor calculator, and the frequency relay requires frequency input. The user must click on the input node of the models to make sure the correct signals are recorded. The relays using signals from other models has default input from models and must be ordered after the model producing the signals. Sorting by order was previously the only option to accomplish this, but ATPDraw v7 offers an option Edit|Arrange|Sort all Models to help ordering correctly. All the relays has a blocking control signal input, trip signal and trip zone information outputs. In the dialog window the user sets the zone characteristics and there is also View option that plots the zones and recorded trajectories (with down sampling) until trip. The W1RELAY21P component also has a zone helper.

 Selection Object name Icon ATP card Description Relays +Overcurrent 50/51 W1RELAY51 MODELS Based on rms input and a definite time zone gives a trip signal out. Blocking option available. Zone output not relevant. Relays +Time over-current W1RELAY51I MODELS Based on rms input and standardized inverse time zone gives a trip signal out. Relays +Dir. Ground 67N W1RELAY67N MODELS Current and voltage input with internal zero sequence phasor calculation. Trips is |V0|>Vlim and I0 in zone relative to V0. Relays + Distance quad 21 W1RELAY21P MODELS Input from RX calculator. Three delayed zones with 4 points. Zone helper available. Relays + Distance circ 21 W1RELAY21C MODELS Input from RX calculator. Three delayed zones with mho characteristic. Relays +Diff transf. 87T W1RELAY87T MODELS Input from current phasors 1+h. Calc. differential current with turns ratio, phase shift scaling and harmonic blocking (inrush). Current into unit on both sides. Relays +Diff line 87L W1RELAY87L MODELS Input from current phasors 1+h. Calc. differential current with time delay compensation and harmonic blocking. Current into unit on both sides. Relays +Under-voltage 27 W1RELAY27 MODELS Input from rms voltage. Two undervoltage zones with time delays and 3 different standard characteristics. Relays +Over-voltage 59 W1RELAY59 MODELS Input from rms voltage. Two overvoltage zones with time delays and 3 different standard characteristics. Relays +Frequency 81 W1RELAY81 MODELS Input from frequency calculator. Two zones for both under and over frequency with fixed time delay.

TACS

 Selection Object name Icon ATP card Description TACS +RMS TABC2RMS TACS 3-phase RMS calculator. DEVICE66 TACS +Freq TABC2FRQ TACS 3-phase frequency calculator. DEVICE50 TACS +DQ0 TABC2DQ0 TACS 3-phase park transform calculator. TACS +alpha-beta TABC2ABG TACS 3-phase alpha-beta transform calculator.