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To enable simpler modelling of a network, it is possible to apply a transformer with load as an element at a node. In load flow calculations, the transformer load provides insight into the secondary voltage, and saves one node each time.

 

The load and generation can be given in four different ways (P,Q,I,S, cos phi). The button Appearance is used to switch between them, and convert parameters.

 

 

PARAMETERS

 

General

 

 

Simultaneousness

The stated load is multiplied by the simultaneousness factor g. This is given in the node form and applies for the load part of all transformer loads present at the node. See also: Simultaneousness

The generation and PV in the transformer node are not multiplied with the simultaneousness factor.

 

Behaviour

A pre-defined load behaviour can be selected under behaviour. This load behaviour is also applicable for the generation.

 

Growth

Seven fixed growth scenarios are built into Vision: No growth, 1%, 1.5%, 2%, 3%, 4% and 5%, exponentially per year. In addition, a user can define a custom growth scenario.

 

Profile

At profile a defined profile can be selected.

 

Transformer

 

 

1)   The prime winding default voltage corresponds the corresponding node nominal voltage.

 

Type

The type list contains all transformers from the component type database whereby Unom,w1 lies between 0.8*Unom and 1.2*Unom of the node. See also: Type

 

Tap changer

The designation of the tap position can be fully defined by the user by indicating the minimum, nominal and maximum tap. Take care that the minimum tap, for example, is defined as the tap with the smallest number of windings, and thus gives the greatest transfer ratio (depending on the tap side).

 

Copy and paste type data

Transformer and transformer load type data can be copied and pasted by right mouse clicking on the component's type data form. A pop-up menu appears with Copy type data and Paste type data. The copied data can be used for a new or an existing transformer (load). This can be helpful when a transformer has to be changed into a transformer load or vice versa.

 

Connection

 

 

Reliability

 

 

Harmonics

 

 

Current and angle:

The harmonic current injection is related to the nominal current in percent:

Current(h) = I(h) / I(1) x 100%

 

The angle of the harmonic current injection is related to the angle of the voltage in the nominal loadflow situation:

Angle(h) = Angle(h) - Angle(1), in degree

 

Customers

 

 

MODELLING

 

Load flow

After completion of the load flow calculation, the secondary voltage is calculated using the calculated load current, the impedance of the transformer, and the tap setting. The behaviour of the load is dependent on the voltage and defined in Behaviour. Modelling of the load is described under: Load behaviour

 

IEC 60909

In IEC 60909 calculations, the transformer load is not taken into consideration. Zero sequence impedances of the transformer are also not taken into consideration with asymmetrical short-circuits.

 

Fault analysis

In the sequential fault analysis, the transformer load is modelled as a normal load impedance, without taking account of the influence of the transformer. The impedance is determined using the pre-fault node voltage and load current, determined in advance by means of a load flow calculation.

In the case of asymmetrical faults, zero sequence impedances of the transformer are not taken into consideration.

 

Costs

The transformer load is not involved in the cost calculation.

 

Reconfiguration of a transformer load

A transformer load can be decomposed into a transformer, a secondary node and a load. All properties are transformed into the new configuration. Select the transformer load and choose: Start | Edit | Split.