NEPLAN Reliability Analysis

Reliability Analysis module is used to determine the frequency, average duration and cost of network component failures, leading to supply interruptions. Analysis takes into consideration the outage behaviour of network equipment (failure rate and repair times), the network operation in normal state and for multiple order network contingencies. Admissible short-time component overloading are also accounted for. Realistic generation patterns and load curves are used while the module implements a protection concept including protection failures.

Contingencies dealt with can be stochastic failures or overlapping independent stochastic failures, common-mode failures, protection failure or overfunction, multiple earth faults, spontaneous protection tripping, or failure occurring during the maintenance of the backup components.

 Applications

• Optimal asset allocation and cost-benefit analysis for investments in transmission and distribution networks
• Design and evaluation of innovative substation layouts
• Weak-point analysis in existing networks
• Design of automation concepts in public and industrial distribution networks
• Detailed and objective discussion of network connection concepts for high-demand customers and power plants
• Cost-effective mitigation of power quality problems (voltage sags)
• Add-on for NEPLAN-Main – a tool to apply Reliability Centred Maintenance (RCM) Strategy, which leads to substantial reduction of maintenance expenses

Results

Result values are printed at load nodes in network graph, which can be colour shaded according to the Reliability Analysis outcome.  Results are fully exportable for use in tables and diagrams and comprise of:

• Frequency of supply interruptions
• Probability of supply interruptions
• Mean interruption durations
• Energy not served in time
• Interruption cost

Evaluation Functions

Reliability Analysis module provides various flexible filter and diagram functions to visualize results and facilitate analysis:

• Consideration of power/energy-specific interruption cost
• Filter to investigate component contributions to load node interruptions
• Shading of network diagram in dependence of load node results
• Analysis of system reaction after faults
• Copying of diagrams into clipboard

Reference: NEPLAN

NEPLAN Harmonic Analysis

Harmonic Analysis can be performed in 3-phase, 2-phase, 1-phase AC systems to test the operating behaviour of the networks at frequencies above 50/60 Hz. The module can be used to compute the network impedance and harmonic level for each frequency and for each node as well as the frequency response of meshed networks. The results can be displayed both in the frequency and time domain and serve as basis for the planning of ripple control systems, dimensioning of compensators (SVC) and harmonic filters, determination of network impedance for sub-synchronous resonance or filter design.

General Characteristics

• U-I and I-U sensitivity for each frequency
• Distributed parameter line model applied
• Frequency-dependence of elements is considered. Libraries available
• Automatic frequency step length control during impedance computation to detect resonances
• Calculation in the positive component system (symmetrical) or in the phase system
• Calculation of self- and mutual line impedances in function of the frequency
• Harmonic load flow (P, Q, I, U, losses)
• Results in frequency or time domain

Harmonic Levels

This module computes current and voltage at all frequencies and at all predefined nodes and elements as well as the r.m.s. values for harmonic voltages and currents with fundamental harmonic voltage or current taken from the Load flow (optional). Results are automatically entered in the single line diagram. Harmonic Analysis module also provides comparison of computed harmonic levels with the limit values laid down in any standards desired.

• Computation of total harmonic voltage factor in conformity with DIN/IEC and distortion factor in accordance with IEEE
• Computation of telephone parameters (TIF, IT, KVT) or transformer k-factor
• List output of ripple control currents and voltages at any desired frequencies and at each node and each element
• Harmonic sum calculation: vectorial, geometric, arithmetic, acc. to IEC 1000-2-6

Harmonic source

Harmonic sources (current and voltage sources) are entered directly in the single line diagram. They can be assigned directly to loads or any power electronic elements, such as Converter, SVC, PWM, etc. Libraries are available. Unlimited number of harmonic sources (current/voltage) can be computed with each harmonic, while any harmonic can be handled, e.g. inter-harmonics due to saturation effects.

Filter Dimensioning

Filter elements are dimensioned directly by NEPLAN and are transferred automatically into the single line diagram.

• Filter elements: filters (normal, HP, C-filter), series RLC-circuits with or without earth connection, ripple control traps
• Filter data are listed or saved in a text file
• Result lists can be saved in text files or in result files for evaluation by means of spreadsheet programs (like MS-Excel)

Reference: NEPLAN

NEPLAN Optimal Separation Points

Optimal Separation Point module eliminates all network meshes by changing the network topology. From the possible topology states the procedure selects one topology that minimizes network losses, considering all activated constraints and without creating isolated sub-systems.

General Characteristics

• User selects which elements are allowed to be switched off
• Option for prevention of overloaded elements
• Option for prevention of limit violations of node voltages
• User-defined activation and deactivation of constraints used for the optimization

Reference: NEPLAN