Power Systems - Contingency Analysis

Table of contents

Introduction

Contingency analysis is an essential method for bolstering the reliability and stability of contemporary power systems by detecting and mitigating potential failures in advance. Modern electrical grids are intricate, interconnected networks where the failure of a single component can disrupt voltages, power flows, and equipment loading across the entire system. By assessing system responses to such disturbances, engineers pinpoint vulnerabilities and optimize operational reliability.

In power systems, a contingency is an unexpected event, such as a transmission line tripping, a transformer outage, or a generator disconnection from the network. Contingency analysis quantitatively assesses system performance after such occurrences by recalculating bus voltages, power flows, and equipment loading based on revised operational conditions. Engineers systematically compare simulation results to operational thresholds, including bus voltage limits and thermal loading constraints for transmission lines and transformers.

N-1 analysis is a prevalent form of contingency analysis where the system is evaluated for the loss of a single component at a time. Although the grid may seem stable during routine operation, contingency analysis reveals latent vulnerabilities that are exposed only during equipment outages. These assessments enable utilities and system operators to mitigate cascading failure risks, refine planning, and uphold secure operation under varied conditions.

Contingency Analysis Using PandaPower

Here is a 5 step process to perform an N-1 analysis using PandaPower:

• Step 1. load grid into network
• Step 2. define limits
• Step 3. loop through each line and set ‘in_service’ to false
• Step 4. run pandapower on network and compare system values against limits
• Step 5. hightlight elements that exceed limits

The python code will look something like:

Step 1 - Loading a network

import pandapower as pp
import pandapower.networks as nw
import pandapower.plotting as pplt
import matplotlib.pyplot as plt

net = nw.create_cigre_network_mv() # use example network cigre

Step 2 - Defining limits

# Line limits
vmax = 1.05
vmin = 0.95
max_ll = 100

for line in net.line.index:
    net.line.at[line, "in_service"] = False
    pp.runpp(net)