Free Expert Guides on Power Systems, Circuit Design & Electrical Troubleshooting

Hi everyone, I’m Oliver, and I’ve been working in the instrument transformer industry for almost eight years now. From a complete newbie to someone who can now handle things independently, I’ve participated in dozens of combined instrument transformer inspections over the years.Today, I’d like to share with you: What tests must a qualified combined instrument transformer go through before leaving the factory or being put into operation? After all, it's a v

To ensure safe operation of the power system, power equipment operation must be monitored/measured. General devices can’t connect to primary high - voltage equipment directly; instead, large primary currents are scaled down for current transformation, electrical isolation, and use by measurement/protection devices. For AC large - current measurement, conversion to a unified current eases secondary instrument use.Current transformers split into measurement - and protection - type, with

Hey everyone! I’m Oliver, an experienced electrician with over a decade in the power system industry. Today, we’re diving into a practical topic — what tests are required to ensure an Air Insulated Switchgear (AIS) voltage transformer is qualified? These tests are crucial not only for ensuring the device operates correctly but also for maintaining the safety and stability of the power grid. Let’s get started!1. Visual InspectionFirst Look MattersThe very f

Hey everyone, I’m Oliver, a 10-year veteran in the power system industry. Today we’re going to talk about a very practical topic — how do you know if a current transformer (CT) used in Air Insulated Switchgear (AIS) is truly qualified? This isn’t just about meeting technical specs; it’s directly tied to equipment safety, grid stability, and accurate metering.Let’s dive in — based on my real-world experience.IntroductionIn subs

1. IntroductionOutdoor voltage transformers are key equipment for ensuring the safety of electrical apparatus. Scientific and comprehensive test analysis is required to avoid hazards and property losses caused by improper operation. Test analysis can guide the formulation of operation strategies and precautions, ensure the stable operation of equipment, and maximize economic and social benefits.2. Concept of Outdoor Voltage TransformersAn outdoor voltage transformer is essentially an outdoor ste

Hey everyone, I'm Oliver, and I've been working with current transformers (CTs) and voltage transformers (VTs) for 8 years.From assisting my mentor on site to leading high-voltage testing teams and conducting error calibrations independently, I’ve dealt with all kinds of instrument transformers — especially those used in GIS systems. The error test for voltage transformers is something I perform regularly.A few days ago, a friend asked me: “Oliver, how exactly do yo

In UHV GIS, current transformers are key to electric energy metering. Their accuracy determines power trade settlements, so on - site error verification perJJG1021 - 2007is needed. On - site, use power supplies, voltage regulators, and current boosters. Due to encapsulation in GIS, build test circuits via exposed grounding knives, bushings, and return conductors; right circuits simplify wiring and boost accuracy.Challenges like large test current, long circuits, and high impedance exist, but rea

I’m Oliver, an 8 - year current transformer testing pro. Today, let’s break down new and old polarity test methods for GIS current transformers—how they work and their pros/cons.1.Testing Methods1.1New Method Pre - test ops: Open FDS21/FDS22 fast disconnectors + DS23 disconnector. Close CB21 breaker, then ES21/ES22 grounding disconnectors. Disconnect ES21’s SF6 - shell ground. Wiring: Connect battery between ES21’s moving contact (negative ground

Fellow electric power calibration workers, you must have encountered this situation: The nameplate of an outdoor current transformer has been tormented by wind, sun, rain, and freezing, to the point where the transformation ratio is indistinguishable! Don't panic, we have a solution - use a current transformer calibrator and through the “transformation ratio trial calibration method”, we can figure out the actual transformation ratio and errors clearly. Here, taking the SHGQ

By Oliver, 8 Years in the Electrical IndustryHi everyone, I'm Oliver, and I've been working in the electrical industry for 8 years.From early days doing substation equipment commissioning to now managing protection and metering configurations for entire distribution systems, one of the most frequently used devices in my work has been the Current Transformer (CT).Recently, a friend who's just starting out asked me: “How do you test current transformers? Is there a simple and effective w