VipCrop

Visually Interactive Package for Load Flow, Fault Current Calculation and Relay Settings for HT Network Operation and Planning

VipCrop is a distribution system simulator modeling a HT network at different voltage levels from 400 V, 3.3 kV, 6.6 kV, 11 kV, 22 kV to 66 kV. This versatile distribution system simulator integrates load flow, fault current calculation and modeling of overcurrent relays and breaker operation. The simulator implements full graphic display of the network superimposed with the calculated line flow during normal condition, and the calculated fault current flow and breaker tripping time during fault conditions.

In contrast with the conventional load flow and fault current calculation programs, VipCrop enables the user to operate a circuit breaker, activate a fault, start a motor, or change a transformer’s tap-ratio. The immediate effects of the user’s operation are modeled and the calculated results are visually displayed on the single-line diagram similar to the real time display of operating a network in a control center. In addition, while operating the system, the user can visually modify the network such as adding a new bus, a new line or changing the settings of a particular relay. Thus, it serves as a very useful tool for both network operation and network planning.

1.       VISUALLY INTERACTIVE MODELING

Once a specified network is loaded, load flow will be calculated automatically. The load flow can be displayed in MW and MVar, or MVA and amperes. The voltage at each node can also be displayed in kV or in per-unit of the rated voltage. If there is an excessive overload on a particular circuit, the breaker may trip and the relay operating time is shown. Due to the operation or tripping of a breaker, a new load flow is automatically calculated and displayed. Three standard types of IDMT relays based on BS 142 are modeled. Additional relay types such as 1.3/10, DTL, high set and unit protections are also available.

Clicking on a busbar. The user only has to click on the network elements to change their status or characteristics. By simply right clicking on a busbar, a pop-up menu will appear for the user to activate a list of items:

Clicking on a Breaker.  By simply right-clicking on a breaker, the user may close, open or block a breaker. The user may either view or update the settings of the overcurrent relay connected to a breaker. The settings consist of current transformer ratio, plug setting, TMS setting, relay type and high set operating current.

Line and Transformer. By moving the mouse pointer to a line, the line ID, rating, length, type of cable, and the R, X and B will be shown on the pre-allocated panel. By clicking on a transformer, the user may change the transformer tap position, which is constrained within its maximum and minimum tap ratio limits.

Dynamic Mismatch Management. Due to the change in the network topology or parameters, the load flow calculation may not be converged. In this case, the mismatch tolerance is automatically doubled until a convergent solution is found. If however, the mismatch exceeds 1 MW, the program will terminate the calculation and display the convergent network prior to the last network modification.

 Relay Movements at Fault. Once a fault is activated at a particular bus or line, the program calculates the 3-phase fault current distribution and models the operation of all the relays and breakers. Once a breaker has tripped, the fault current calculation is repeated until the fault has been isolated. A post fault load flow will then be conducted automatically.

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2.       MAIN APPLICATIONS

Distribution Loss and Motor Starting. The user may examine the results of load flow calculation for a number of different networks given by VipCrop.  The user may alter various network parameters to assess circuit loading, distribution loss, power factor improvement and the starting of large HT motor.

Assessment of Relay Settings. Overcurrent relays are usually graded according to a radial network. Can these relays operate with adequate discrimination during fault and overload conditions when the network is operated in a ring configuration or interconnected with two or three sources? What will be the sequence of tripping and the degree of the loss of supply? Queries on these operational problems can be verified by using VipCrop in one single run. The user may also vary the setting scheme to achieve minimum supply interruption during various fault conditions. Prior to the fault, each breaker can be blocked to simulate the breaker or relay failure so that the effect of the upstream relay operation can be assessed.

Network Security Assessment. VipCrop can be used to assist engineers to verify whether supply to the whole area can be restored under various feeder outages or overload conditions.  The engineer may also make use of this simulator to work out standard procedures or rules for the restoration of supply for each abnormal case well in advance.

Evaluation of Network Proposals. VipCrop can be used to evaluate each distribution network proposal under normal, fault and overload conditions. The level of reliability and its operation constraints and limits can be compared easily through simulation.

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3.       OBJECT ORIENTED NETWORK EDITOR

Dynamic network Creation and Modification. A built-in network editor is provided for the user to create a new network or to modify an existing network. The user may simply pick a desired voltage button and then click on the canvas. A rectangular busbar symbol will appear together with a pop-up form for the user to enter the name of the bus, the connected load and shunt reactive component. The user may simply pick the line button and then click the first bus and then the second bus. A line will automatically connect the two buses with a pop-up form for the user to pick the type and length of cable. The circuit parameters such as R, X and B will be automatically calculated and entered to the built-in file. Similar arrangements are provided for the user to connect a transformer a bus-coupler, a generator and a transformer. At any time the user may re-arrange the network by simply clicking a bus and move to a new location and all the line connected to the bus will be automatically adjusted. A bus or a line may be deleted and the corresponding network parameters will be automatically updated.

lternative Structured Data input. Tabulated data are also provided to list the complete network parameters grouped under busbar, line, transformer and incoming sources. The user may view or change any value in the tabulated data without going to the network diagram.

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4.       RELATED PUBLICATION

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5.       LICENSE AND FEE

VipCrop is available under a single license for a single copy price of S$6,800.  Support and updates are provided free of chargé for 12 months.

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6.       HOW TO ORDER

Make bank cheque in Singapore dollars payable to Byte Power Publications and post to 10 H, Braddell Hill, #23-30, Singapore 579727. VipCrop with a  user’s guide will then be delivered.

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7.      TYPICAL DISPLAY

* Click on the thumbnails below for sample display

    For supply fed by in-plant generators, the starting of a 6.6 KV 600 KVA motor at MT6 causes excessive voltage drops in the whole network. The user attempts to change the transformer tap changer position from 1.0 to 0.95.

    Using the object oriented network editor, the user clicks feeder F6, selects from a list of standard circuits and then simply enter the length in Km and the R, X and B will be automatically calculated and entered to the built-in file structure.

    Fault current at each line , relay movements and fault voltages are shown. Subject to a current of 1586 A, the two breakers which have the lowest settings are tripping.

    The fault at Bus 4 is isolated by the tripping of six breakers at 0.73, 1.04 and 1.31 seconds. At the post fault load flow, the user views/changes the settings of the breaker at Bus 13.

    Assessing of large HT motor on bus MSW.

    Due to error in relay setting, the cable fault causes the loss of supply of eight substations.

    The line power flow  displayed in MW and Mvar.

    Viewing of Bus Fault in Amps.

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Last modified: 04/09/09