# UCTE-DEF

## Introduction

The Union for the Co-ordination of Transmission of Electricity, created in 1951, coordinated the operation and development of the electricity transmission grid for the Continental European synchronously operated transmission grid, thus providing a reliable platform to all participants of the Internal Electricity Market and beyond.

In 1999, UCTE re-defined itself as an association of TSOs in the context of the Internal Energy Market. Building on its experience with recommendations, UCTE turned to make its technical standards. These standards became indispensable for the reliable international operation of the high voltage grids which are all working at one “heart beat”: the 50 Hz UCTE frequency related to the nominal balance between generation and the electricity demand of some 500 million people in one of the biggest electrical synchronous interconnections worldwide.

On 1 July 2009 UCTE was wound up. All operational tasks were transferred to ENTSO-E.

## Format specifications

The UCTE-DEF (UCTE Data Exchange Format) format is an exchange format specified by the UCTE, for the exchange of grid model among its members. The data refer to load flow and three phase short circuit sudies and describe the interconnected extra high voltage network. The data are contained in an unformatted standard US ASCII file. The file is divided into 7 different blocks:

• Nodes (N)
• Lines (L)
• Two windings transformers (T)
• Two windings transformers regulation (RR)
• Two windings transformers special description (TT)
• Exchange powers (E)

Each block is introduced by a key line consisting of the two characters ## and of the character given above in brackets. The end of a block is given by the next key line or the end of the file. The information of the each block is written in lines and the contents are separated by a blank (empty space).

The grid is described in Bus/Branch topology, and only few types of equipments are supported (nodal injections, AC line, two windings transformer). Fictitious nodes are located at the electric middle of each tie line. The defined X-nodes are binding for all users.

### File name convention

The UCTE-DEF format use the following file name convention: <yyyymmdd>_<HHMM>_<TY><w>_<cc><v>.uct with:

• yyyymmdd: year, month and day
• HHMM: hour and minute
• TY: the file type
• FO: Day ahead congestion forecast
• 2D: 2-days ahead congestion forecast
• SN: Snapshots
• RE: Reference
• LT: Long-term reference
• 0123: Intra-day ahead congenstion forecast. The value is the number of hours separating the case date and the generation date.
• w: day of the week, starting with 1 for Monday
• cc: The ISO country-code for national datasets, UC for UCTE-wide merged datasets without X nodes and UX for UCTE-wide merged datasets with X nodes
• v: version number starting with 0

The specifications of the UCTE-DEF format are available online.

## Import

The import of a UCTE file into an IIDM grid model is done in three steps. First, the file is parsed and a UCTE grid model is created in memory. Then, some inconsistency checks are performed on this model. Finally, the UCTE grid model is converted into an IIDM grid model.

The UCTE parser provided by PowSyBl does not support the blocks ##TT and ##E providing respectively a special description of the two windings transformers and the scheduled active power exchange between countries. Those blocks are ignored during the parsing step.

### Inconsistency checks

Once the UCTE grid model is created in memory, a consistency check is performed on the different elements (nodes, lines, two windings transformers and regulations).

In the tables below, we summarize the inconsistency checks performed on the network for each type of equipment. For the sake of clarity we use notations that are made explicit before each table.

#### Nodes with active or reactive power generation

Notations:

• $$P$$: active power generation, in MW
• $$Q$$: reactive power generation, in MVar
• $$minP$$: minimum permissible active power generation, in MW
• $$maxP$$: maximum permissible active power generation, in MW
• $$minQ$$: minimum permissible reactive power generation, in MVar
• $$maxQ$$: maximum permissible reactive power generation, in MVar
• $$Vreg$$: voltage regulation, which can be enabled or disabled
• $$Vref$$: voltage reference, in V
Check Consequence
$$Vreg$$ enabled and $$Q$$ undefined $$Q = 0$$
$$P$$ undefined $$P = 0$$
$$Q$$ undefined $$Q = 0$$
$$Vreg$$ enabled and $$Vref$$ undefined or $$\in [0, 0.0001[$$ Node type = PQ
$$minP$$ undefined $$minP = -9999$$
$$maxP$$ undefined $$maxP = 9999$$
$$minQ$$ undefined $$minQ = -9999$$
$$maxQ$$ undefined $$maxQ = 9999$$
$$minP > maxP$$ $$minP$$ switched with $$maxP$$
$$minQ > maxQ$$ $$minQ$$ switched with $$maxQ$$
$$P > maxP$$ $$maxP = P$$
$$P < minP$$ $$minP = P$$
$$Q > maxQ$$ $$maxQ = Q$$
$$Q < minQ$$ $$minQ = Q$$
$$minP = maxP$$ $$maxP = 9999$$ and $$minP = -9999$$
$$minQ = maxQ$$ $$maxQ = 9999$$ and $$minQ = -9999$$
$$maxP > 9999$$ $$maxP = 9999$$
$$minP < -9999$$ $$minP = -9999$$
$$maxQ > 9999$$ $$maxQ = 9999$$
$$minQ < -9999$$ $$minQ = -9999$$

#### Lines or two-windings transformers

Notations:

• $$X$$: reactance in $$\Omega$$
Check Consequence
$$X \in [-0.05, 0.05]$$ $$X = \pm 0.05$$
Current limit $$<0$$ Current limit value ignored

#### Regulations

##### Phase regulation
Check Consequence
Voltage value $$<=0$$ Voltage value set to NaN
Invalid ($$n = 0$$) or undefined ($$n$$, $$n’$$ or $$\delta U$$) data provided Regulation ignored
##### Angle regulation
Check Consequence
Invalid ($$n = 0$$) or undefined ($$n$$, $$n’$$ or $$\delta U$$) data provided Regulation ignored
Undefined type type set to ASYM

### From UCTE to IIDM

The UCTE file name is parsed to extract metadata required to initialize the IIDM network, such as its ID, the case date and the forecast distance.

#### Node conversion

There is no equivalent voltage level or substation concept in the UCTE-DEF format, so we have to create substations and voltage levels from the nodes description and the topology. Two nodes are in the same substation if they have the same geographical spot (the 1st-6th character of the node code) or are connected by a two windings transformer, a coupler or a low impedance line. Two nodes are in the same voltage level if their code only differ by the 8th character (bus bars identifier).
Note: We do not create a substation, a voltage level or a bus for X-nodes. They are converted to dangling lines.

For nodes with a valid active or reactive load, a load is created. It’s ID is equal to the ID of the bus post-fixed by _load. The P0 and Q0 are equal to the active load and the reactive load of the UCTE node. For those with a valid generator, a generator is created. It’s ID is equal to the ID of the bus post-fixed by _generator. The power plant type is converted to an energy source value (see the mapping table below for the matching).

Mapping table for power plant types:

UCTE Power plant type IIDM Energy source
Hydro (H) Hydro
Nuclear (N) Nuclear
Lignite (L) Thermal
Hard coal (C) Thermal
Gas (G) Thermal
Oil (O) Thermal
Wind (W) Wind
Further (F) Other

The list of the power plant types is more detailed than the list of available energy source types in IIDM, so we add the powerPlantType property to each generator to keep the initial value.

#### Line conversion

The busbar couplers connected two real nodes are converted into a switch. This switch is open or closed depending on the status of the coupler. In the UCTE-DEF format, the coupler can have extra information not supported in IIDM we keep as properties:

• the current limits is stored in the currentLimit property
• the order code is stored in the orderCode property
• the element name is stored in the elementName property

The lines connected between two real nodes are converted into a AC line, except if its impedance is too small (e.g. smaller than 0.05). In that particular case, the line is considered as a busbar coupler, and a switch is created. The susceptance of the UCTE line is splitted in two, to initialize B1 and B2 with equal values. If the current limits is defined, a permanent limit is created for both ends of the line. The element name of the UCTE line is stored in the elementName property.

The lines connected between a read node and an X-node are converted into a dangling line. In IIDM, a dangling line is a line segment connected to a constant load. The sum of the active load and generation (rep. reactive) is computed to initialize the P0 (resp. Q0) of the dangling line. The element name of the UCTE line is stored in the elementName property and the geographical name of the X-node is stored in the geographicalName property.

#### Two windings transformer conversion

The two windings transformers connected between two real nodes are converted into a two windings transformer. If the current limits is defined, a permanent limit is created only for the second side. The element name of the transformer is stored in the elementName property and the nominal power is stored in the nominalPower property.

If a two windings transformer is connected between a real node and an X-node, a fictitious intermediate voltage level is created, with a single bus called an Y-node. This new voltage level is created in the same substation than the real node. The transformer is created between the real node and the new Y-node, and the X-node is converted into a dangling line. The only difference with a classic X-node conversion, is that the electrical characteristic are hold by the transformer and set to 0 for the dangling line, except for the reactance that is set to $$0.05\space\Omega$$.

TODO: insérer un schéma

##### Phase regulation

If a phase regulation is defined for a transformer, it is converted into a ratio tap changer. If the voltage setpoint is defined, the ratio tap changer will regulate the voltage to this setpoint. The regulating terminal is assigned to the first side of the transformer. The ρ of each step is calculated according to the following formula: $$\rho = 1 / (1 + i * \delta U / 100)$$.

##### Angle regulation

If an angle regulation is defined for a transformer, it is converted into a phase tap changer, with a FIXED_TAP regulation mode. ρ and α of each step are calculated according to the following formulas:

• for an asymmetrical regulation (e.g. $$\Theta \ne 90°$$)
$\begin{array}{ccl} dx & = & step_i \times \dfrac{\delta U}{100} \times \cos(\Theta) \\[1em] dy & = & step_i \times \dfrac{\delta U}{100} \times \sin(\Theta) \\[1em] \rho & = & \dfrac{1}{\sqrt{dy^2 + (1 + dx)^2}} \\[1em] \alpha & = & - \text{atan2}(dy, 1 + dx) \\[1em] \end{array}$
• for a symmetrical regulation (e.g. $$\Theta = 90°$$)
$\begin{array}{ccl} dx & = & step_i \times \dfrac{\delta U}{100} \times \cos(\Theta) \\[1em] dy & = & step_i \times \dfrac{\delta U}{100} \times \sin(\Theta) \\[1em] \rho & = & 1 \\[1em] \alpha & = & - 2 \times \text{atan2}(dy, 2 \times (1 + dx)) \\[1em] \end{array}$

Note: The sign of $$\alpha$$ is changed because the phase tap changer is on side 2 in UCTE-DEF, and on side 1 in IIDM.

## Export

TODO

### Options

These properties can be defined in the configuration file in the import-export-parameters-default-value module.

ucte.export.naming-strategy
The ucte.export.naming-strategy property is an optional property that defines the naming strategy to be used for UCTE export.

Its default value is Default, which corresponds to an implementation that expects the network elements’ ID to be totally compatible with UCTE-DEF norm (e.g. a network initially imported from a UCTE-DEF file), and throws an exception if any network element does not respect the norm. It does not do any ID modification.