A voltage sag or voltage dip is a short-duration reduction in the voltage of an electric power distribution system. It can be caused by high current demand such as inrush current or fault current elsewhere on the system.

In general, IEC standards define how power quality is measured (which is based on physics), whereas regional or country specific regulations define the normal limits (which is a political choice).

See:

IEC 61000-4-30 ... Power quality measurement methods

IEC TS 62749:2020 Assessment of power quality - Characteristics of electricity supplied by public networks

EN 50160 is a European standard that defines, describes and specifies the main characteristic of the voltage at a network user’s supply terminals in public low voltage, medium and high voltage AC electricity networks under normal operating conditions.

A first step to solving the issue is for the utility to temporarily install PQ meters to identify which circuits have load switching operations that are causing the sags. A second step is then to fit correction equipment and/or re-engineer the local power system.

Various organizations offer products and services for this, for example:

This technical note summarizes the EN50160 data and statistics measured by the PowerLogic™ ION™ meters that monitor compliance to the EN51060:2010 standard, and includes references to the applicable parts of IEC 61000-4-30

https://www.se.com/ww/en/download/document/7EN72-0197/

Voltage sag is an reduction of rms value of voltage magnitude which is more than 0.1 pu. This reduction is of short duration around half a cycle.

Happy New Year to you too! When it comes to the voltage sag problem in power systems, the International Electrotechnical Commission (IEC) has defined standards that address this issue. According to IEC standards, voltage sag is typically defined as a decrease in voltage from 10% to 90% of the nominal voltage, lasting for a duration of up to 3 minutes. However, IEC standards do not explicitly specify the frequency of sag occurrences in terms of how often they can happen per hour, per day, or per year. In practice, voltage sags can occur around 2 to 3 times per day, lasting for approximately 200 milliseconds, and sometimes even for longer durations. It's important to consult specific regional or national standards and regulations for more detailed information on voltage sag requirements and frequency limits in your particular jurisdiction.

Voltage sag, also known as voltage dip or voltage drop, refers to a temporary reduction in the voltage level in a power network. The standards that define voltage sag characteristics and the acceptable limits vary across different countries and regions. Here are some commonly referenced standards:

It is important to note that these standards are periodically updated, and different countries or regions may have their own specific standards and regulations related to voltage sag. Local electrical utility companies and regulatory bodies often establish guidelines and limits to ensure the reliability and quality of power supply within their respective jurisdictions. Therefore, it is recommended to refer to the relevant standards and regulations specific to your country or region for comprehensive and up-to-date information on voltage sag standards.