OeS software

OeS 6 software is intended for modeling and calculation of radial and multiply closed power networks, under operating and short-circuit conditions. The program’s computational capabilities allow for the analysis of the operation of HV, MV and LV networks within one model. The program is also equipped with modules supporting the selection of protection settings and determining the load capacity of cables depending on the installation conditions. OeS has always been created as an engineering tool – it is characterized by transparency and simplicity of use, while maintaining a full range of computational functionalities for the implementation of analytical and design tasks.

Individual OeS software modules allow you to perform power flow and short-circuit calculations, which are an indispensable element of every project or connection expertise. Available functionalities enable, among others: proper selection of devices with regard to operation in operating and short-circuit conditions, solving problems related to reactive power compensation or assessment of the operation of the neutral point. They also support planning the expansion of the existing network and help in making connection decisions. In the OeS software, you can quickly perform calculations for any network configuration, which opens up great opportunities for users to create multi-variant analyses.

Functionalities related to modeling and analysis of network security operation have also been developed for many years. The user can analyze the sensitivity and selectivity of protections, determine their response times, and assess the risk of shock. Additionally, OeS can be equipped with the PROKAB module, which allows for the creation and calculation of the longitudinal and transverse profiles of the cable and the determination of substitute parameters for overhead lines. Another additional element is the GRAFIK module, which allows for the modeling of consumers taking into account the variability of the load over time (operator’s tariff or measurement data) and the modeling of prosumers taking into account the variability of their generation. The possibility of using the ENTSO-E database (climate years) has been implemented here, taking into account the weather forecast in the calculations or entering measurement data. Computational functionalities allow for the analysis of time histories of power and branch currents, voltages in network nodes, losses and other network parameters.

Line profile and cable ampacity

Graphical analysis

Short circuits

Calculations in disturbance states include:

calculations of symmetrical short-circuit current parameters,
calculation of the parameters of the minimum symmetrical short-circuit current,
calculations of symmetrical short-circuit current flow,
calculations of asymmetric short-circuit current parameters,
calculations of asymmetrical short-circuit current flow.

The methodology for calculating short-circuit currents is based on the standard PN-EN 60909-0 – for symmetrical short-circuits and PN-EN 60909-3 – for asymmetrical short-circuits.

Calculations of short-circuit currents are made based on an appropriately constructed equivalent network diagram. In this diagram, there is a substitute voltage source at the fault site and network elements presented in the form of impedance doubles. The substitute voltage source is the only active source in the diagram and replaces all real sources. The sources of short-circuit current include: the supply network, generators, synchronous and asynchronous motors and equivalents of substitute networks.

Calculations of symmetrical short-circuit current parameters

In the calculation of the symmetrical short-circuit current parameters, a short-circuit is assumed in each analyzed node and the characteristic parameters of the short-circuit current flowing to that node are determined.

The analysis of exceedances consists in checking the elements according to the given strength:

surge – applies to busbars and connectors, exceeding the limit parameters is checked, i.e. peak current i_por surge current i_p
switching – applies to switches, the maximum breaking current I_cuis checked for exceeding the symmetrical short-circuit breaking current of 20 ms calculated for a given element,
thermal – applies to power lines, busbars and connectors, exceeding the thermal short-circuit current I_thr is checked.

Additionally, when analyzing exceedances for power lines, the temperature increase of the current path during a short circuit is also determined.

All calculated parameters have been grouped in the result window and are visible in tabs, as shown below:

Fault current parameters tab:
- nominal voltage U_n(kV) – nominal voltage (voltage level) of the network in which a given node is located,
- initial short-circuit current I_k” (kA) – modulus of the resultant complex value of the short-circuit current, calculated for all sources, I_k” = | ΣI_k”_i|
- total initial short-circuit current according to the share of sources ΣI_k” (kA) – the sum of the modules of the complex values of individual short-circuit currents flowing to the short-circuit location from each source, ΣI_k ” = Σ|I_k”_i|,
- short-circuit power S_k” (MVA),
- surge short-circuit current i_pA(kA) – the κ coefficient determined for the ratio R/X of the resultant impedance of the network affected by the short circuit is assumed, method in accordance with the standard,
- surge short-circuit current i_pB(kA) – the value of the κ coefficient is assumed increased by 15% compared to that calculated in method A, the method recommended according to the standards for closed networks; in which high heterogeneity causes the R/X relations in individual branches of the replacement scheme to be different,
- surge short-circuit current i_pC(kA) – is the sum of the components calculated for each short-circuit current source separately, based on a different coefficient κ – depending on the R/X ratio of a particular branch of the equivalent circuit; the most accurate method, but non-normative,
- short-circuit breaking current for 20 ms I_b20(kA) – symmetrical,
- short-circuit breaking current for 50 ms I_b50(kA) – symmetrical,
- short-circuit breaking current for 100 ms I_b100(kA) – symmetrical,
- short-circuit breaking current for 250 ms I_b250(kA) – symmetrical,
- aperiodic component of the short-circuit current for a time of 20 ms and_DC20(kA) – aperiodic component current,
- aperiodic component of the short-circuit current for a time of 50 ms and_DC50(kA) ) – aperiodic component current,
- aperiodic component of the short-circuit current for 100 ms and_DC100(kA) ) – aperiodic component current,
- aperiodic component of the short-circuit current for a time of 250 ms and_DC250(kA) ) – aperiodic component current,
- asymmetrical short-circuit breaking current for 20 ms I_basym20(kA) – I_b supplemented by i_DC,
- asymmetrical short-circuit breaking current for 50 ms I_basym50(kA) – I_b supplemented by i_DC,
- asymmetrical short-circuit breaking current for 100 ms I_basym100(kA) – I_b supplemented by i_DC,
- asymmetrical short-circuit breaking current for 250 ms I_basym250(kA) – I_b supplemented by i_DC,
- steady-state short-circuit current I_k(kA),
- equivalent thermal current for a given short-circuit time – value determined on the basis of the coefficients m and n I_{th (t s)}(kA),
- equivalent thermal current for a given short-circuit time converted to 1 s I_thr(1s)(kA),
- equivalent thermal current for a given short-circuit time converted to a time of 3 s I_thr(3s)(kA),
Potential exceedances tab:
- - busbar surge current or switch peak current i_pr(kA) – basis for determining the exceedance of the surge strength,
  - impact load degree i_p/i _pr(%),
  - exceeding (impact strength) – signals exceedance when (i_p/i_pr)> > 100%,
  - maximum breaking current of the switch I_cu(kA) – basis for determining the switching strength,
  - connector load degree I_b/I_cu(%),
  - exceeding (connective strength) – signals exceedance when (I_b/I_cu)> > 100%,

Full calculation results are available in the result window. All calculated parameters have been grouped there (due to the type of result and the analyzed short circuit) and are visible in tabs, as shown below:

- - node results:
    - nominal network voltage U_n(kV),
    - zero sequence voltage U₀(kV),
    - positive sequence voltage U₁(kV),
    - negative sequence voltage U₂(kV),
    - L1 phase voltage U_L1(kV),
    - L2 phase voltage U_L2(kV),
    - L3 phase voltage U_L3(kV),
  - branch results:
    - nominal voltage of the branch U_n(kV),
    - zero sequence short-circuit current I₀(kA),
    - positive sequence short-circuit current I₁(kA),
    - negative sequence short-circuit current I₂(kA),
    - L1 phase short-circuit current I_L1(kA),
    - L2 phase short-circuit current I_L2(kA),
    - L3 phase short-circuit current I_L3(kA),

Analysis of exceedances

The OeS 6 program enables variant analysis of the operation of the modeled network in terms of exceeding the limit parameter values and determining the minimum and maximum values of parameters characterizing the network. For this purpose, the network operation variants intended for such analysis should be previously defined.

Full analysis results are available in the result window. It presents the minimum and maximum values of characteristic parameters and exceedances of limit parameters along with the configuration variant for which they occurred. All calculated parameters are grouped in the result window (depending on the type of result and the selected type of calculation) and are visible in tabs as shown below:

- - Flow Calculations tab:
    - Nodal Results tab:
      - minimum voltage |U|_min(kV),
      - variant – name of the variant in which the minimum voltage in the node was found,
      - maximum voltage |U|_max(kV),
      - variant – name of the variant in which the maximum voltage in the node was found,
    - Branch Results tab:
      - minimum current |I|_min(A),
      - variant – name of the variant in which the minimum current in the branch was found,
      - maximum current |I|_max(A),
      - variant – name of the variant in which the maximum current in the branch was found,
      - minimum calculated load level I_d%min(%) – only for transformers and power lines for which the long-term permissible current has been defined,
      - variant – name of the variant in which the minimum calculated load level was found,
      - exceeding – signals an exceedance when I_d%min> 100%,
      - maximum calculated load level I_d%max(%) – only for transformers and power lines for which long-term permissible current has been defined,
      - variant – name of the variant in which the maximum calculated load level was found,
      - exceeding – signals an exceedance when I_d%max> 100%,
  - Fault current parameters tab:
    - Initial short-circuit current tab:
      - nominal voltage U_n(kV),
      - minimum initial short-circuit current |I _k”|_min(kA),
      - variant – name of the variant in which the minimum value of the initial short-circuit current was found,
      - maximum initial short-circuit current |I _k”|_max(kA),
      - variant – name of the variant in which the maximum value of the initial short-circuit current was found,
    - Short circuit power tab:
      - nominal voltage U_n(kV),
      - minimum short-circuit power |S_k”|_min(MVA),
      - variant – name of the variant in which the minimum value of short-circuit current or power was found,
      - maximum short-circuit power |S_k”|_max(MVA),
      - variant – name of the variant in which the maximum value of short-circuit current or power was found,
    - Surge current tab:
      - nominal voltage U_n(kV),
      - minimum surge current |i_pC|_min(kA),
      - variant – name of the variant in which the minimum value of the surge current was found,
      - maximum surge current |i_pC|_max(kA),
      - variant – name of the variant in which the maximum value of the surge current was found,
    - Thermal short-circuit current tab for a short-circuit duration of 0.1 s:
      - nominal voltage U_n(kV),
      - minimum thermal short-circuit current for a short-circuit time of 0.1 s I_th(t)min(kA),
      - variant – name of the variant in which the minimum value of thermal short-circuit current was found for a short-circuit duration of 0.1 s,
      - maximum thermal short-circuit current for a short-circuit time of 0.1 s I_th(t)max(kA),
      - variant – name of the variant in which the maximum value of thermal short-circuit current was found for a short-circuit time of 0.1 s,
    - Short-circuit breaking current tab for a short-circuit duration of 250 ms:
      - nominal voltage U_n(kV),
      - minimum symmetrical breaking current for a short-circuit time of 250 ms I_b250min(kA),
      - variant – name of the variant in which the minimum value of the symmetrical breaking current was found for a short-circuit time of 250 ms,
      - maximum symmetrical breaking current for a short-circuit time of 250 ms I_b250max(kA),
      - variant – name of the variant in which the maximum value of the symmetrical breaking current was found for a short-circuit time of 250 ms.

OeS software

Short circuits

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