Tech Express

The Structure of Micro Precision Current Transformers
Jul 15, 2026

A Micro Precision Current Transformers consists of a primary winding, a secondary winding, an iron core, insulation between the windings and the core, and a casing. Micro precision current transformers used to commonly use 1J85 splashed ink alloy wound into a ring-shaped iron core, but thanks to the industry development, currently those Micro Precision Current Transformers mainly use of nanocrystalline core. Common pressure pressed thin strips models include 1k107 and 1k107B. If the Micro precision current transformers performance requirements are not high, silicon steel sheets and ferrites can be used as a replacement choose. The advantage of a ring-shaped magnetic core is that it has no air gap and good magnetic properties. Especially if the winding is uniform during the winding process, the leakage magnetic flux is very small. The insulation between the ring core and the winding is generally achieved by adding a plastic protective shell to the core. The protective shell has two functions, insulation and protection of the core, which the protection of the core is the most important. The core material is highly sensitive to stress, and its magnetic properties will change when subjected to stress. Adding a protective shell can reduce stress during winding, thus it is important to handle the transformer with care during production. However, ultrafine crystalline materials are already very brittle and require even more protection. After winding the windings, the transformer is encapsulated in the casing. Of course, there will be many inspection processes throughout the entire production process. Micro current transformers are divided into single turn and multi turn types according to the primary winding. The primary winding of a single turn miniature current transformer has only one turn. Rod type: Steel tube copper bars are integrated with the transformer housing through the iron core window (such as micro current transformers used in some electronic meters). Busbar type: The iron core window is retained, and the busbar passes directly through the iron core window. For measuring small currents, the busbar can also be wound around the iron core window for 2 or 3 turns to obtain a smaller current ratio. Multi turn miniature current transformers have multiple turns of primary winding, such as the 103105 series current type miniature voltage transformers. The function of potting adhesive is to encapsulate and insulate, and the commonly used material is epoxy resin+curing agent.
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The Working Principle of Current Transformer
Jul 22, 2026

In the power supply lines, there is a huge difference in current and voltage, ranging from a few amperes to tens of thousands of amperes. For the convenience of secondary instrument measurement, it is necessary to convert the current into a relatively uniform current. In addition, the voltage on the circuit is relatively high, making direct measurement very dangerous. The current transformer plays a role in current conversion and electrical isolation. Previously, most display instruments were pointer type current and voltage meters, so the secondary current of current transformers was mostly in ampere level. Nowadays, most electricity measurement is digitized, and the sampling signal of computers is generally in the milliampere range (e.g. 0-5V, 4-20mA). The secondary current of micro current transformers is in the milliampere range, mainly serving as a bridge between large transformers and sampling. Miniature current transformers are also known as "instrument current transformers". The term "instrument current transformer" refers to a multi current ratio precision current transformer used in laboratories, generally used to expand the instrument range Principle circuit diagram of current transformer Miniature current transformers work similarly to transformers based on the principle of electromagnetic induction. Transformers convert voltage, while miniature current transformers convert current. As shown in the diagram, winding N1 is connected to the measured current, which is called a set of windings (or primary winding, primary winding); Connect winding N2 to the measuring instrument and become the secondary winding (or secondary winding, secondary winding). The current ratio between the primary winding power I1 and the secondary winding I2 of a miniature current transformer is called the actual current ratio K. The current ratio of a miniature current transformer when operating at the rated working current is called the rated current ratio of the current transformer, expressed in Kn. Kn=I1n/I2n Micro current transformers can be roughly divided into measuring current transformers and protective current transformers. A. Measurement current transformer The measuring current transformer is mainly used in conjunction with measuring instruments to measure current, voltage, power, etc. under normal operating conditions of the circuit. The main requirements for measuring micro current transformers are: 1. Reliable insulation; 2. High enough measurement accuracy; When a high current occurs due to a fault in the side line, the transformer should saturate within an appropriate 20% (such as 500% of the rated current) to protect the measuring instrument. B. Protective current transformer The protective current transformer is mainly used in conjunction with the relay device to provide a signal to the relay device to cut off the faulty circuit in case of short circuit overload or other faults, in order to protect the safety of the power supply system. The working conditions of protective miniature current transformers are completely different from those of measuring transformers. Protective transformers only start working effectively at currents several times or tens of times higher than normal. The main requirements for protective transformers are: 1. Reliable insulation; 2. A sufficiently large accurate limit coefficient, 3. Adequate thermal and dynamic stability. The maximum primary current that the protective transformer can meet the accuracy level requirements under rated load is called the rated accuracy limit primary current. The accurate limit coefficient is the ratio of the rated accurate limit current to the rated primary current. When the current is large enough, the iron core will saturate and cannot reflect the current. The accurate limit coefficient represents this characteristic. The accuracy level of the protective transformer is 5P and 10P, indicating that the allowable error at the rated accuracy limit for one current is 5% and 10%. When a fault occurs in the circuit, the surge current generates heat and electromagnetic force, and the protective current transformer must withstand it. The effective value of the primary current that a current transformer can withstand without damage within one second in the event of a short circuit in the secondary winding is called the rated short-time current. The peak value of the primary current that the current transformer can withstand without damage in the event of a short circuit in the secondary winding is called the rated dynamic stability current. Protective current transformers are divided into: Overload protection current transformer Differential protection current transformer Grounding protection current transformer (zero sequence current transformer) C. Micro voltage transformer Micro voltage transformers, due to size and manufacturing reasons, usually use current type voltage transformers. In fact, it is a current transformer with a rated current ratio of 1 and both primary and secondary currents in milliampere level (e.g. 2mA/2mA): During operation, the primary winding of the transformer is connected in series with the current limiting resistor R to measure the voltage, and the secondary output is connected to the operational amplifier for I/V conversion (or direct resistance sampling). At this point, the primary current is I1=U (R+r), and the secondary current I2=I1/Kn, where r is the internal resistance of the primary winding and Kn is the rated current ratio.
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Current Transformer Error
Jul 29, 2026

Reasons for errors In fact, there must be energy loss during the operation of the current transformer, which causes errors in the current transformer. To generate current in the secondary winding, an excitation current I0 is required to excite and generate induced potential and current. The excitation current is provided by the primary winding. The product I0W1 of the excitation current I0 and the number of turns W1 of the primary winding is called the excitation ampere turn or excitation electromotive force. It means that the first winding turns need to be deducted from the example turns before they are transmitted to the first winding, resulting in errors. The error is caused by providing excitation turns. The error of current transformers consists of two parts: non ratio difference and phase difference. It should be noted that the transformer ratio is the percentage of the secondary current error value to the actual primary current, not the percentage of the rated current. This is different from the method of expressing the error of other general measuring instruments as a percentage of fullness (% F.S). There is no concept of full capacity for current transformers, only the measurement range and rated current. For example, a micro transformer with an accuracy level of 0.1 has an allowable ratio difference of+/-0.1% at 100% rated current and+/-0.4% at 5% rated current. Assuming the rated current is used as the full scale, the allowable ratio difference at 100% rated current is expressed as a percentage of full scale, which is+/-0.1% F.S. The allowable ratio difference at 5% rated current is expressed as a percentage of full scale, which is+/- (0.4x5%/100%)%=+/-0.02% F.S Error compensation of current transformer Current transformers without compensation have negative specific differences and positive angular differences. The allowable range of error for current transformers at all levels is positive and negative deviation. Therefore, the surplus range of positive and negative deviations can be utilized to improve the accuracy of the transformer. In order to improve the accuracy of transformers, various compensation methods are generally used. In general, due to the small compensation value, it can be considered that the magnetic field of the iron core should not be abstracted. This can be calculated using error superposition. The compensation methods for current transformers include turn compensation, auxiliary iron core compensation, capacitor compensation, etc. Turn compensation The compensation method for the number of turns of micro current transformers is the simplest, as long as the secondary winding is wound Nx fewer than the rated number of turns. The ratio difference before compensation of the current transformer is replicated, and increasing the current of the secondary winding by fewer turns serves as compensation. The compensation amount is as follows: △f=Nx/(N2-Nx)x100% The ratio difference of the turns compensation team plays a compensating role, and the compensation amount is independent of the secondary load and current size. The compensation turns are generally only a few turns, and the turn compensation should calculate the error between the maximum current low-end secondary impedance and the minimum current high-end secondary impedance. Du Yu's high-precision micro current transformer can compensate for excessive turns even if it only compensates for one turn. At this point, half turn or fractional turn compensation can be used. However, the number of turns of a current transformer is calculated based on the closed circuit passing through the iron core window, and the number of turns of a current transformer is calculated by smashing one by one, without the situation of half a turn. The use of half turn or fractional turn compensation requires the use of auxiliary terminals, such as dual windings, dual iron cores, etc. Auxiliary iron core compensation The auxiliary iron core compensation has a compensating effect on the contrast difference and angle difference, but the manufacturing process of the auxiliary iron core compensation method is relatively complex. Capacitor compensation Capacitor compensation can be achieved by directly connecting capacitors in parallel at both ends of the secondary winding of the current transformer. Its contrast difference plays a positive compensation role, and the compensation size is proportional to the X component in the secondary load Z=R+iX, and proportional to the size of the compensation capacitor; It has a negative compensation effect on the cross, and the compensation size is proportional to the R component in the secondary load Z=R+iX, and proportional to the size of the compensation capacitor. Capacitor compensation is an ideal compensation method. In micro precision current transformers, the secondary winding is generally directly connected to the current/voltage conversion of the operation and discharge, and the secondary impedance is basically 0. At this time, the role of capacitor compensation is relatively small. Generally, adding a phase shift circuit in the interpretation of current/voltage conversion can solve the angle difference problem. Users can adjust and calculate the phase shift circuit based on the error data of the voltage reduction in the inspection report of the current transformer that comes with it when it leaves the factory. There are many compensation methods for current transformers. The compensation of current transformers is an important way to improve the accuracy level of current transformers, and one of the important tasks in designing high-precision current transformers.
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5 Key Parameters to Check When Buying a Current Transformer | Ultimate Guide
Sep 09, 2026

Introduction Current transformers act as the sensory core of every power distribution system. Their performance directly impacts metering accuracy and the reliability of relay protection systems. Whether you’re designing a new industrial power project, upgrading distribution cabinets, or replacing aging CT units, checking these five critical parameters upfront helps you Pick the right current transformer (CT), avoid on-site debugging headaches and costly post-installation replacements. 1. Transformation Ratio (CT Ratio) The transformation ratio is the fundamental specification of current transformer. It defines the conversion rate between high primary operating current and the standardized low secondary current. In the power industry, 1A and 5A secondary outputs are the universal standard, fully compatible with most smart meters, protection relays, and data sampling devices on the market. When selecting a CT ratio, the key is matching it to the circuit’s typical long-term operating current. Over-sizing the ratio forces the CT to operate under light load, weakens measurement precision, and makes it impossible to capture subtle current variations. An undersized ratio leads to continuous overload operation, which accelerates core wear and shortens the device’s service life. Practical Tip:Choose a CT ratio that makes the circuit’s normal operating current fall between 60% and 80% of the CT’s rated primary current for the best measurement linearity. 2. Accuracy Class A CT’s accuracy class dictates its measurement precision and applicable working scenarios. A common mistake is mixing up metering and protection class CTs, which leads to mismatched performance, faulty data, and system malfunction. These two CT types are engineered for completely different purposes and cannot be used interchangeably. Metering-class CTs are optimized for daily current monitoring and energy metering. Standard accuracy grades include 0.2S, 0.5S, 0.2, and 0.5. High-precision 0.2S and 0.5S models are widely adopted in grid metering and commercial power measurement, where strict error control is mandatory for billing and data statistics. Protection-class CTs, marked 5P or 10P, are built specifically for power system fault conditions. Instead of prioritizing daily measurement precision, they focus on maintaining stable, linear output during short-circuit surges and extreme current fluctuations to ensure protection relays trigger correctly. Practical Tip: Never use protection-class CTs for precise metering, and avoid metering-class CTs for primary protection loops — each has its exclusive working scenario. 3. Rated Burden Rated burden is the top cause of core saturation and current waveform distortion in field applications. Measured in VA (Volt-Amperes), rated burden refers to the maximum secondary load a CT can handle while retaining its certified accuracy level. The total secondary burden covers all load components in the closed CT loop: cable wiring resistance, terminal contact resistance, and power consumption from connected devices like meters, relays, and sampling boards. If the actual on-site burden exceeds the CT’s rated value, secondary voltage spikes will occur, triggering core saturation, distorted current output, and significant measurement errors. Practical Tip: Always reserve a 20%–30% safety margin during selection. Keep actual operating burden below 75% of the CT’s rated burden to accommodate future wiring adjustments, device additions, and long-term operational changes. 4. Insulation Level & Voltage Rating Current transformers are designed for specific voltage grade systems, so matching the correct insulation and voltage rating is fundamental to safe operation. Low-voltage 0.66kV CTs are standard for industrial distribution cabinets, while medium and high-voltage models are customized for substation and grid-level power systems. Superior insulation performance enables CTs to resist overvoltage shocks, lightning surges, and long-term electrical aging. In harsh industrial environments with frequent voltage fluctuations, high humidity, or heavy dust, insufficient insulation will cause creepage, insulation breakdown, and even permanent device burnout. Practical Tip: For harsh industrial and outdoor scenarios, choose CTs with enhanced insulation ratings to boost operational stability and extend service life under extreme working conditions. 5. Working Environment & Mechanical Specifications Environmental adaptability and mechanical dimensions determine a CT’s long-term operational stability. If it cannot adapt to on-site installation and environmental conditions even a perfectly parameter-matched CT will fail early. First, verify the operating temperature range. Standard indoor CTs cannot withstand extreme high or low temperatures. Outdoor and heavy-duty industrial CTs feature wider temperature tolerance to prevent performance drift and parameter deviation under harsh weather conditions. Second, confirm installation dimensions and aperture size. The CT’s inner diameter must perfectly fit the primary busbar or cable to ensure accurate current induction and smooth installation. An ill-fitted aperture will compromise sensing performance and cause unstable measurement data. Additionally, for sites with strong electromagnetic interference, mechanical vibration, or corrosive substances, select fully sealed CTs with anti-interference and corrosion-resistant housings to minimize failure rates and improve operational reliability. Summary Selecting a qualified current transformer is far more than simple parameter matching — it requires comprehensive evaluation of application scenarios, on-site circuit conditions, and operating environments. CT ratio and accuracy class lay the foundation for basic working performance, rated burden guarantees long-term linear operation, insulation ratings ensure system safety, and mechanical & environmental specifications determine equipment durability. By verifying these five key parameters before purchasing, you can effectively avoid metering errors, protection system failures, and premature equipment aging. This simple pre-purchase check ensures stable, reliable, and long-term operation of your entire power monitoring and protection system. Contact us to get customized solution / Request datasheet
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How to Determine the Burden of a Current Transformer
Sep 02, 2026

Introduction Current transformers (CT) are core components for current measurement, energy metering, and relay protection in power systems. “Burden” is one of the most critical parameters for a current transformer. Incorrect burden matching will cause waveform distortion, large measurement errors, inaccurate energy-meter reading, or even failure of protection relays. Understanding how to calculate and select a proper CT burden is essential for stable power‑system operation. Here we explain CT burden fundamentals, calculation steps, common pitfalls and practical selection guidelines for engineers. 1. What is Current Transformer Burden? CT burden refers to the total apparent power (unit: VA, Volt‑Ampere) consumed by all secondary‑side connected components at rated secondary current. It represents the total load on the CT secondary winding. The secondary‑side load includes: Internal resistance of CT secondary winding Resistance of connecting wires / cables Impedance of connected devices: ammeters, energy meters, protection relays, sampling circuit boards Formula: Burden can also be expressed in ohms(Ω). Conversion between VA and ohms is frequently used in engineering practice. 2. Why Burden Matching Matters Too small actual burden The CT works under light load. For measuring‑class CTs, accuracy can stay within specification. However, for protection‑class CTs, excessively low burden may alter saturation characteristics under fault conditions. Too large actual burden (over‑burden) This is the most‑common field issue: 1. Secondary voltage rises, magnetic core saturates 2. Output current waveform distorts 3. Measurement error increases, metering data deviates 4. Protection CT fails to correctly reflect fault current, leading to protection mal‑operation or refusal‑to‑operate Rule: The calculated actual circuit burden must be less than or equal to the rated burden marked on the CT nameplate. 3. Step‑by‑Step: Calculate Actual Secondary Burden Step 1: Confirm CT rated secondary current Two mainstream standards: 5A secondary output (widely used in traditional power cabinets) 1A secondary output (long‑distance wiring scenarios, reduces wire power consumption) Step 2: Sum impedance of all secondary‑side devices Check datasheet for each connected instrument / PCB sampling unit for its power consumption or impedance value. Example: Energy meter burden consumption: 1.5 VA Protection relay: 2.0 VA Sum all individual device VA values. Step3: Calculate wire burden Copper connecting cables contribute significant burden, especially for long wiring distance. Wire resistance formula: - ρ: Resistivity of copper conductor - L: One‑way cable length between CT and load device - A: Cross‑sectional area of copper wire Note: CT secondary forms a closed loop, so round‑trip length (2L) shall be adopted. Wire burden: Step4: Get total actual burden Total Actual Burden = Sum of instrument burden + Wire burden Step5: Compare with CT rated burden Requirement: Actual total burden ≤ CT rated burden on nameplate. Keep reasonable margin; it is recommended actual burden ≤75% of rated burden for reliability margin. 4. Practical Engineering Examples Case parameters CT rated secondary current: 5A Rated burden on nameplate: 10 VA Connected loads: Energy meter 2 VA, current indicator 1 VA Copper wire: 1.5 mm², one‑way length L=20 m 1. Sum instrument burden: 2 VA +1 VA = 3 VA 2. Compute round‑trip wire resistance and wire burden 3. Total actual burden = instrument burden + wire burden 4. Compare against CT rated 10 VA, verify margin. If calculated actual burden exceeds rated burden, feasible solutions: 1. Increase copper wire cross‑section, reduce wire resistance 2. Select CT with higher rated burden 3. Change to 1A secondary‑current CT to cut wire loss for long‑distance transmission 5. Common Misunderstandings 1. Ignore cable burden: Engineers only consider instrument VA, neglect long‑cable impedance, resulting in hidden over‑burden. 2. Confuse burden class and accuracy class: 0.5, 0.2S represent accuracy; burden(VA) represents load capacity. A high‑accuracy CT still fails when over‑burdened. 3. Multiple devices series connection: Each additional device adds burden; do not cascade unlimited instruments on one CT secondary loop. 4. Secondary open‑circuit risk: While calculating burden, remember CT secondary circuit must never be open‑circuited. Open circuit produces extremely high dangerous voltage and damages the magnetic core. 6. Quick Selection Checklist for CT Burden Record rated secondary current (1A /5A) Collect power consumption of every secondary‑connected device Measure actual wiring length, calculate copper wire burden Sum to get total actual burden Actual burden ≤ CT rated burden, retain 20‑30% design margin Re‑check when modifying cabinet wiring or adding secondary devices Conclusion Determining CT burden is not merely reading nameplate parameters; it requires full calculation of instruments plus wiring impedance. Reasonable burden matching guarantees measurement precision and reliable protection action for your power‑monitoring hardware. When designing current‑sampling hardware including zero‑sequence CT and ordinary current transformers, always run burden calculation at the design phase, rather than adjusting after on‑site faults For more information discuss, please contact us freely.
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Zero Sequence CT vs Ordinary Current Transformer: Differences & Selection Guid
Aug 26, 2026

Introduction Current transformers (CT) are essential sensing parts in power systems. Zero-sequence CT and conventional ordinary CT both rely on electromagnetic induction, yet they differ greatly in structure, working logic and usage. Choosing the correct model directly determines the stability of power measurement, protection and electrical fire monitoring systems. Core Differences 1. Working Principle Ordinary CT It measures the current of a single independent phase cable passing through the core. It converts large load current into standard small secondary current for metering, overload and short-circuit protection. Under normal three-phase operation, each CT independently outputs the corresponding phase current signal. Zero Sequence CT All three live wires (A/B/C) and neutral wire pass through one core together. When the three-phase current is balanced, the vector sum \(I_a+I_b+I_c=0\), and the CT outputs no current. Once insulation leakage or single-phase ground fault occurs, residual zero-sequence current generates magnetic flux inside the core, triggering leakage alarm and grounding protection. 2. Structural Design Ordinary CT: Single-hole structure, one CT corresponds to only one phase cable; silicon steel cores are commonly used. Zero-sequence CT: Large-diameter annular core, allowing 3 phases + N wire to pass through simultaneously; mostly adopts high-permeability nanocrystalline cores to capture tiny mA-level leakage current accurately. Split-type zero-sequence CT supports live installation without power interruption. 3. Application Scenarios Ordinary CT Three-phase electric energy metering, cabinet load monitoring, motor overload & short-circuit protection, current sampling for inverters and charging piles. Zero Sequence CT Electrical fire monitoring, low-voltage leakage protection, photovoltaic combiner box ground fault protection, anti-electric shock safety protection for industrial and building power distribution systems. 4. Sensitivity & Features Ordinary CT focuses on measuring large working current with low sensitivity and cannot detect micro leakage. Zero-sequence CT stays zero-output under balanced load, features ultra-high sensitivity, and is specially designed for weak leakage fault detection. Comparison Table Item Ordinary CT Zero Sequence CT Detection object Single-phase load current Residual zero-sequence current Wiring rule One phase per CT ABC+N pass through one core Main material Silicon steel sheet Nanocrystalline alloy Core use Metering, overcurrent protection Leakage monitoring, fire prevention Selection Tips 1). For power statistics, load monitoring and phase short-circuit protection: adopt ordinary single-phase CT, 3 units for a three-phase loop. 2). For leakage early warning, electrical fire prevention and grounding fault protection: select zero-sequence CT. 3). For old power system reconstruction without power cut: choose split open-type CT. Conclusion Ordinary CT realizes measurement and overload protection for power equipment, while zero-sequence CT undertakes safety defense against leakage and grounding accidents. Matching the two types properly can build a complete power safety system covering metering, overload protection and fire prevention. Our factory provides customized split zero-sequence CT, miniature precision CT and three-in-one integrated current transformers, adaptable to power distribution, new energy, fire monitoring and other industrial scenes. For more information, please contact us for details discuss.
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Common backup battery types for CT power take-off devices
Aug 12, 2026

With the rapid development of the Power Line Communication and Smart Grid, current transformer power take-off technology has become the mainstream power supply method for line monitoring equipment due to its advantages of no additional wiring and convenient installation. However, CT power has a flaw called the 'low current dead zone'. When the line load is extremely low or power outage, the induced current is insufficient to maintain the operation of the equipment. Thus, a reliable backup battery becomes the key solution to ensure that data is not lost and communication is not disconnected. Here, let's learn about the common types of backup batteries and their key parameters in CT power harvesting devices. 1. Why does the CT power take-off device have to be equipped with a battery? The principle of CT energy harvesting: obtain energy from high-voltage wires throgh electromagnetic induction. Its output power is proportional to the square of the line current. When the current is high: the energy is sufficient, even can battery charge. When low current or no load: the induced voltage dropping, once there is no battery support, the monitoring device will instantly power off and restart, resulting in loss of historical data and communication interruption. Therefore, the backup battery is not only a "spare tire", but also a "stabilizer" for the system. 2. Main backup battery options There are three main battery solutions available on the market to meet the working environment requirements of large temperature differences, difficult maintenance, long lifespan for outdoor power equipment: A). Lithium thionyl chloride battery (Li/SOCl2 Battery) - with a long lifespan, it is currently the preferred choice for high-end power monitoring equipment. Characteristics: Extremely high energy density and low self discharge rate (annual self discharge<1%). Advantages: Wide working temperature range (-55°C~+85°C), floating charging life >10 years, suitable for installation on high-altitude and difficult maintain lines. Disadvantage: Weak instantaneous high current discharge capability, usually requiring parallel capacitors to support the instantaneous transmission of wireless modules. B). Lithium iron phosphate battery (LiFePO4 Battery) -- balance safety and cycling. If the CT power take-off device is frequent charging and discharging mode, this lithium iron phosphate is a excellent choice. Features: Long cycle life (over 2000 cycles), high safety, and good high temperature resistance. Advantages: Compared to ordinary lithium batteries, it is more resistant to overcharging and over-discharging. compared to conventional combinations (12.8V) and (14.4V),it has a more stable voltage platform (3.2V). Disadvantage: The low-temperature performance is relatively weak, and it needs to be used in conjunction with heating circuits in extremely cold areas. C). Super capacitors (SC) -- Strictly speaking, they are not batteries. They have good instantaneous explosion effects,which often used as auxiliary energy storage in CT power harvesting. Features: Extremely fast charging and discharging speed, almost infinite cycle life. Advantage: Perfectly solve the high current demand of wireless communication module transmission. Disadvantage: Low energy density, unable to maintain device standby for a long time, usually combined with lithium-ion batteries to form a "hybrid energy storage system". 3. How to choose the appropriate battery? When choosing a backup battery, you cannot only consider the capacity, but also the following four parameters: A). Voltage platform and cut-off voltage The CT power module requires a stable DC voltage (such as 12.8V or 14.4V). Attention: Lithium ion batteries are rated at 3.6V and lithium iron phosphate at 3.2V. When selecting, it is necessary to confirm whether the power management circuit (PMU) supports this voltage range and whether the cut-off voltage will cause the device to shut down abnormally. B). Capacity unit: mAh or Ah. Calculation formula: Battery capacity>(device average power consumption x Min. power outage time)/ discharge depth. For example, if the average power consumption of the device is 100mW and it is required to maintain operation for 24 hours after a power outage, considering the conversion efficiency, at least a high-capacity battery pack needs to be equipped. C). Pulse discharge capability Power monitoring equipment usually wakes up and reports data at regular intervals. At the moment of GPRS/4G transmission, the current may reach 2A. Key point: The battery must be able to withstand this pulse without generating excessive voltage sag, otherwise it will cause the device to reset. D). Wide temperature performance Power equipment installed outdoors, the temperature inside the box can reach 70°C+ under direct sunlight in summer, and -30 °C in northern in winter. Requirement: The battery must be able to charge and discharge normally within the range of -40 °C to+75°C, and must not leak or explode at high temperatures. Battery Type Energy Density Cycle Life Safety Application Li/SOCl2 Battery ⭐⭐⭐⭐⭐ ⭐⭐⭐ ⭐⭐⭐ Low power consumptionlong lifespandifficultly maintain scenarios LiFePO4 Battery ⭐⭐⭐ ⭐⭐⭐⭐⭐ ⭐⭐⭐⭐ Frequent charging and discharging scenarios with high safety requirements Super capacitors ⭐ ⭐⭐⭐⭐⭐ ⭐⭐⭐⭐⭐ Auxiliary power supply to solve the problem of instantaneous high current emission Application Suggestion: For CT power supply devices, the most ideal solution is often a hybrid mode of "lithium sub battery (lithium iron phosphate)+supercapacitor". Lithium ion batteries are responsible for long-term standby and low current loads, while supercapacitors are responsible for absorbing surge energy from CT and assisting wireless transmission. If you have any relevant needs, please feel free to contact us for professional and prompt feedback.
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How to Select the Right Current Transformer for Energy Meters
Aug 05, 2026

Energy meter accuracy depends heavily on the performance of the current transformer (CT). Even a high-precision smart meter will produce inaccurate readings, data drift, or metering errors if matched with an unsuitable current transformer. For smart grid projects, residential metering, commercial power monitoring, and solar energy measurement, selecting the right CT is critical for long-term stable and accurate energy data collection. This guide explains the key factors engineers and buyers must consider when choosing a current transformer for energy meter applications. 1.Priority Accuracy Class for Metering Applications Energy metering requires higher precision than general industrial current monitoring. For standard electricity meters, 0.2 class and 0.5 class CTs are common. For high-precision smart meters, laboratory metering, and grid-grade measurement, 0.1 class or even 0.05 class nanocrystalline current transformers are necessary. Unlike industrial monitoring CTs, metering-grade CTs must maintain low ratio error and low phase error under light load conditions, which is the biggest advantage of nanocrystalline core transformers. 2. Correct Current Ratio Matching The CT primary current must match the actual load current range of the energy meter circuit. If the CT current rating is too large, low current signals will cause severe inaccuracy; if the rating is too small, saturation and waveform distortion will occur under overload conditions. Common metering current ratios include 50A/5A, 100A/5A, 200A/5A, and custom ratios for special smart meter projects. 3. Core Material Determines Long-Term Stability Traditional silicon steel CTs are cheap but perform poorly under tiny current and low-load scenarios. For smart energy meters that require 24/7 long-term operation, nanocrystalline core current transformers are the best solution. Nanocrystalline cores feature ultra-low magnetic leakage, excellent temperature stability, and minimal phase shift, effectively solving light-load inaccuracy and temperature drift problems that plague ordinary CTs. 4. Installation Structure Selection Solid core CT is widely used for factory pre-installed energy meters, offering higher stability and better shielding performance. Split core CT is more suitable for retrofit metering projects, allowing installation without cutting off power, which improves construction efficiency for grid renovation. 5. Compliance with International Standards All meter-level current transformers must comply with IEC 61869 and local grid metering standards to ensure data validity and certification pass rate. Conclusion To achieve accurate energy metering, you must match the correct accuracy class, current ratio, core material, and structure according to your meter type and application environment. High-quality nanocrystalline metering CTs greatly improve the reliability of smart meter data. Contact us to get professional CT selection guidance, free samples, and customized current transformer solutions for your energy meter projects.
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