Calculations > Fault Analysis

Fault analysis

Calculate | Basic | Fault analysis is used to perform a sequential fault analysis. Note:

•A sequential fault analysis is always started using Calculate | Basic | Fault analysis | Start

•A sequence may consist of:

oa fault at a node;

oa fault to a cable or overhead line

oa fault at an element

oopening a switch connected to a branch or an element.

After each sequence, all node voltages, branch currents and element currents are recalculated.

The features of the Calculate | Basic | Fault analysis menu item are described below.

Start

When Calculate | Basic | Fault analysis | Start is selected, the "pre-fault" voltages in the nodes are calculated as a starting point for the fault analysis. These voltages are determined by performing a load flow calculation. The load flow is performed with 100% load and generation. Transformer regulation is switched off and shunt regulations are on.

When starting the calculation, a check is performed to determine whether the clock numbers of the transformers are not in conflict with each other.

After starting, the program enters sequencing mode.

Fault impedance

With Calculate | Basic | Fault analysis | Fault a fault can be made at a node, in a branch or in an element. An fault impedance can be indicated as well as the fault distance for cables/connections. The impedance at the fault consists of an impedance between the phases (Zpp) and an impedance between phase and earth (Zpe). The impedances are:

•phase-earth: Zpe between a phase and earth

•phase-phase earth: Zpp between two phases and Zpe between two phases and earth

•phase phase: Zpp between the phases

•symmetrical: Zpp between the three phases

•symmetrical-earth: Zpp between the three phases and Zpe between the three phases and earth

In case of an fault in an element, it is actually made before the element. This allows the current through the connection cable and protection to be viewed. In the protection calculation this current is applied for the element protection.

In case of a fault in a transformer, it is actually made in the connection cable. Only 0 and 100% are possible as fault distances.

A fault is applied as follows:

•select the node, branch or element in which the fault should be applied

•choose Calculate | Basic | Fault analysis | Fault

•select the desired closure and if necessary indicate an fault impedance and, in the case of a fault in a branch, also the fault distance

Open switch

With Calculate | Basic | Fault analysis | Open switch a switch in a branch or element can be opened. The phases to be opened can be selected here.

The opening of a switch takes place as follows:

•select the branch or element whose switch is to be selected

•choose Calculate | Basic | Fault analysis | Open switch

•choose the desired side, in the case of a branch

•choose the phase (s) to open

A sequential failure analysis always starts with: Calculate | Start | Fault analysis | Start

The start of a new fault analysis calculation can also be performed, by using the speed button or by pressing F9, if the last calculation was also a fault analysis calculation.

Fault analysis: calculation

Fault analysis: calculation