Sai Calculator

SAIFI Calculator

Use this calculator to determine the System Average Interruption Frequency Index (SAIFI) for a power system, a key reliability metric.

(This is the sum of customers affected by each interruption event over the period.)

function calculateSAIFI() { var totalCustomersServed = parseFloat(document.getElementById('totalCustomersServed').value); var sumCustomerInterruptions = parseFloat(document.getElementById('sumCustomerInterruptions').value); var saifiResultDiv = document.getElementById('saifiResult'); // Input validation if (isNaN(totalCustomersServed) || totalCustomersServed <= 0) { saifiResultDiv.innerHTML = 'Please enter a valid and positive number for Total Customers Served.'; return; } if (isNaN(sumCustomerInterruptions) || sumCustomerInterruptions < 0) { saifiResultDiv.innerHTML = 'Please enter a valid non-negative number for Sum of All Customer Interruptions.'; return; } var saifi = sumCustomerInterruptions / totalCustomersServed; saifiResultDiv.innerHTML = '

SAIFI Calculation Result:

' + 'System Average Interruption Frequency Index (SAIFI): ' + saifi.toFixed(3) + ' interruptions per customer' + 'This means, on average, each customer experienced ' + saifi.toFixed(3) + ' interruptions during the specified period.'; } .saifi-calculator-container { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; background-color: #f9f9f9; padding: 25px; border-radius: 8px; box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1); max-width: 600px; margin: 20px auto; border: 1px solid #e0e0e0; } .saifi-calculator-container h2 { color: #2c3e50; text-align: center; margin-bottom: 20px; font-size: 1.8em; } .saifi-calculator-container p { color: #34495e; line-height: 1.6; margin-bottom: 15px; } .calculator-input-group { margin-bottom: 18px; } .calculator-input-group label { display: block; margin-bottom: 8px; font-weight: bold; color: #34495e; font-size: 1.05em; } .calculator-input-group input[type="number"] { width: calc(100% – 22px); padding: 12px; border: 1px solid #ccc; border-radius: 5px; font-size: 1em; box-sizing: border-box; transition: border-color 0.3s ease; } .calculator-input-group input[type="number"]:focus { border-color: #007bff; outline: none; box-shadow: 0 0 5px rgba(0, 123, 255, 0.2); } .input-hint { font-size: 0.85em; color: #6c757d; margin-top: 5px; } .saifi-calculator-container button { display: block; width: 100%; padding: 12px 20px; background-color: #007bff; color: white; border: none; border-radius: 5px; font-size: 1.1em; font-weight: bold; cursor: pointer; transition: background-color 0.3s ease, transform 0.2s ease; margin-top: 20px; } .saifi-calculator-container button:hover { background-color: #0056b3; transform: translateY(-2px); } .calculator-result { margin-top: 25px; padding: 15px; background-color: #e9f7ef; border: 1px solid #d4edda; border-radius: 8px; color: #155724; font-size: 1.1em; line-height: 1.6; } .calculator-result h3 { color: #0f5132; margin-top: 0; margin-bottom: 10px; font-size: 1.4em; } .calculator-result p { margin-bottom: 8px; } .calculator-result strong { color: #0f5132; }

Understanding the SAIFI (System Average Interruption Frequency Index)

The System Average Interruption Frequency Index (SAIFI) is a crucial reliability indicator used by electric utilities to measure the average frequency of sustained interruptions per customer over a predefined period, typically a year. It provides a clear picture of how often an average customer experiences a power outage.

Why is SAIFI Important?

SAIFI is one of the most widely used metrics for assessing the reliability performance of an electrical distribution system. A lower SAIFI value indicates better reliability, meaning customers experience fewer power interruptions. Utilities use SAIFI to:

• Benchmark their performance against industry standards and other utilities.
• Identify areas for improvement in their infrastructure and operations.
• Track the effectiveness of maintenance programs and capital investments.
• Report reliability performance to regulatory bodies and customers.

How is SAIFI Calculated?

The formula for SAIFI is straightforward:

SAIFI = (Sum of All Customer Interruptions) / (Total Number of Customers Served)

Let's break down the components:

• Sum of All Customer Interruptions: This is not simply the number of outage events. Instead, for each interruption event, you count the number of customers affected by that specific event. Then, you sum these counts for all interruption events that occurred within the reporting period. For example, if one event affects 500 customers and another affects 200 customers, the sum of customer interruptions would be 700.
• Total Number of Customers Served: This refers to the total number of customers connected to the system being evaluated during the reporting period.

Example Calculation:

Let's consider a utility serving 50,000 customers over a year. During this period, they experienced the following sustained interruption events:

• Event 1: A transformer failure affected 1,500 customers.
• Event 2: A tree falling on a power line affected 800 customers.
• Event 3: Equipment malfunction at a substation affected 2,200 customers.

First, calculate the Sum of All Customer Interruptions:

Sum = 1,500 (from Event 1) + 800 (from Event 2) + 2,200 (from Event 3) = 4,500 customer interruptions

Now, apply the SAIFI formula:

SAIFI = 4,500 / 50,000 = 0.09 interruptions per customer

This result means that, on average, each customer connected to this utility experienced 0.09 power interruptions during that year. A lower number is always desirable, indicating a more reliable power supply.

Interpreting SAIFI Results

SAIFI values are typically expressed as "interruptions per customer." For instance, a SAIFI of 1.2 means that, on average, each customer experienced 1.2 power interruptions during the measurement period. It's important to compare SAIFI values over time for the same utility or against similar utilities to get a meaningful understanding of performance. Factors like weather, geographical location, and system age can significantly influence SAIFI.