Transformer pressure relief valve role and selection: YSF series details
Date: March 28, 2026 09:18:43
- pressure relief valveIt is an important safety accessory of the oil transformer, when the pressure inside the tank rises abnormally quickly open the pressure relief to prevent the tank from deformation or bursting.
- When the pressure drops to the closing value after the valve is opened, it automatically and reliably closes to maintain the positive pressure state of the tank and prevent the entry of external air, moisture and impurities.
- The suffix letter of the model number (D/K/SK/J/TH/B) determines the functional configuration of the product, reading and understanding the model number is the first step in the correct selection.
- Caliber selection is based on transformer capacity: capacity ≤ 31500kVA Φ80mm, capacity > 31500kVA Φ130mm.
- YSF series pressure relief valves cover the whole range of caliber from Φ25mm to Φ130mm, and are suitable for many types of equipment such as box transformers, fully enclosed transformers, capacitors and so on.
A. What is a transformer pressure relief valve?
The transformer pressure relief valve is a pressure protection device installed on oil-immersed transformers, box-type substations, on-load tap-changers and other oil compartment equipment. Its core function is: when the pressure inside the tank rises sharply due to internal faults (e.g. short-circuit arcing, insulation breakdown, etc.) and exceeds the opening pressure of the valve, it opens quickly and automatically, releasing the over-pressurized gas and oil quickly, so that the pressure inside the tank is quickly reduced, thus preventing the tank from being deformed or bursting due to over-pressurization.
When the pressure in the tank is reduced to the closing pressure value of the pressure relief valve, the valve can be closed reliably and automatically to ensure that a certain positive pressure is always maintained in the tank, effectively preventing the penetration of external air, water and other impurities into the tank and protecting the purity and insulating properties of the insulating oil.
For the model with directional oil spraying function (suffix containing "D"), the transformer oil released when the valve is opened will be sprayed in a specific direction through the fixed oil guiding device, and introduced into the oil collecting tank through the oil guiding pipe to prevent the oil from splashing around, to meet the requirements of fire prevention and environmental protection, and is a necessary configuration for places with intensive personnel or strict fire prevention requirements.
II. Pressure relief valves andGas RelayWhat's the difference?
In operation and maintenance practice, many people easily confuse the pressure relief valve with the gas relay, thinking that they have similar functions, but in fact there are essential differences between the two in the principle of protection, timing of action and the protection object.
| comparison dimension | pressure relief valve | Gas relays (gas relays) |
|---|---|---|
| Protection Principle | Detect the change of oil pressure in the tank, when overpressure, the mechanical opening pressure relief | Detection of gas buildup in the oil or oil flow impingement, triggering an electrical signal |
| Timing of movements | Immediate action when tank pressure exceeds the opening value | Operation when gas or oil flow is abnormal due to internal failure |
| Movement speed | Extremely fast (milliseconds) for sudden internal failures | Relatively slow, more suitable for detecting slow onset faults |
| output signal | Mechanical Pressure Relief Action + Optional Electrical Alarm Signal | Electrical signals (light gas alarm, heavy gas trip) |
| mounting position | Top of gas cap | On the connecting pipe between the transformer tank and the oil conservator |
| Applicable objects | Fully sealed transformers, box transformers, on-load switches, etc. | Common oil-immersed transformers with oil conservator |
| Whether active pressure relief | ✅ Yes, direct oil pressure release | ❌ No, signal only, no direct pressure relief |
The two are usually configured at the same time and complement each other in practice: the gas relay is responsible for detecting slowly accumulating latent faults, while the pressure relief valve plays the last mechanical protective role in the event of sudden serious internal faults leading to a sudden rise in pressure. The pressure relief valve is the only means of pressure protection for a fully sealed transformer, which is of particular importance due to the lack of an oil conservator and the impossibility of installing a gas relay.
Third, YSF series model suffix letters represent what?
The YSF series pressure relief valve model number consists of multiple fields, with each suffix letter representing a specific functional configuration. Reading the meaning of the model number is the basis for placing an accurate order and avoiding selection errors.
以 YSF9-55/130DSKJTHB As an example, the fields are explained below:
| (numeric, data) field | hidden meaning | Example Value Description |
|---|---|---|
| YSF | Pressure relief valves (product series name) | — |
| 9 (digits) | Design number (9th design) | YSF4, YSF8, YSF9, YSF11, etc. indicate different design versions. |
| 55 | Opening pressure in kPa | Common values: 35kPa, 55kPa, 70kPa, 85kPa, 100kPa, 138kPa |
| 130 | Injector caliber in mm | Optional: Φ25mm, Φ50mm, Φ80mm, Φ130mm |
| D | With directional injection | When opened, the oil will be sprayed out in a directional manner and introduced into the oil collection tank, fire prevention and pollution prevention. |
| SK (or KK) | With dual independent electrical alarm signals | Two signals can be independently connected to the protection device and computer management system. |
| K | With single electrical alarm signal | Trigger the electrical signal output after the action and connect to the relay protection circuit. |
| J | With mechanical alarm signal | Mechanical marking bar pops up after the action, easy to identify the action status visually on the spot |
| TH | Version for use in the humid tropics | Materials and seals acclimatized to humid and hot zone environments |
| B | With locking device | Lock the valve during tank oil pressure test to prevent misoperation |
Functional suffixes can be freely combined as required. For example, YSF8-35/50K means pressure relief valve with 8th design, opening pressure 35kPa, injection caliber Φ50mm, and single electrical signal; YSF9-55/80DK adds directional injection function on this basis. Before ordering, it is recommended to check the required functions one by one to avoid omission or multiple selection.
Fourth, how to choose the caliber and opening pressure of the pressure relief valve?
Selection involves two of the most critical parameters: injection caliber and opening pressure. The selection logic for each of the two has its own focus and needs to be determined separately.
Selection of caliber: according to the transformer capacity
The caliber of oil injection determines the pressure relief capacity when the valve is opened, and needs to be matched with the oil volume and capacity of the transformer.The transformer capacity range corresponding to each caliber of YSF series is as follows:
| Injector caliber | Applicable transformer capacity | Typical Application Scenarios |
|---|---|---|
| Φ25mm | Small box-type transformers, hermetically sealed distribution transformers, power capacitors, reactors, etc. | Box-type substation, 10kV distribution transformer |
| Φ50mm | Small and medium-sized oil-immersed transformers, on-load tap-changers | 35kV medium-sized transformers, industrial distribution transformers |
| Φ80mm | Medium and large transformers with capacity ≤ 31500kVA | 110kV main transformer, industrial large-scale specialized transformer |
| Φ130mm | Large transformers with capacity > 31500kVA | 220kV and above main transformer |
For large transformers requiring more than two Φ130mm caliber pressure relief valves, the number of installations can be estimated according to the following formula:Total oil volume (t) ÷ 23 = Φ130mm Number of pressure relief valves(round up the decimals).
Selection of opening pressure: according to the height of the installation position
The opening pressure should be selected by first checking the distance of the installation position (pressure relief valve installation point) from the highest oil level of the tank, H, and then selecting the appropriate opening pressure gear according to the correspondence between the sealing pressure and the installation height. The core principle is:The sealing pressure of the pressure relief valve should be greater than the maximum allowable working pressure of the transformer 5～10kPa., to ensure that the valve does not open by mistake during normal operation.
| Opening pressure (kPa) | Sealing pressure (kPa) | Maximum height of mounting position H (m) |
|---|---|---|
| 35 | 21 | 1.41 |
| 55 | 33 | 2.63 |
| 70 | 42 | 3.57 |
| 85 | 51 | 4.51 |
| 100 | 60 | 5.40 |
For example, if the pressure relief valve is installed at 2m from the highest oil level of the tank, according to the above table, the opening pressure should be 55kPa (corresponding to the maximum installation height of 2.63m), and the sealing pressure of the 55kPa stage is 33kPa, which is able to ensure that it will not be activated by mistake during normal operation.
V. Main technical parameters of Φ80mm and Φ130mm caliber
The following are the detailed performance parameters of YSF9 series Φ80mm and Φ130mm caliber pressure relief valves for engineering selection reference:
| Parameter items | Φ80mm (YSF9-80K) | Φ130mm (YSF9-130K) |
|---|---|---|
| Effective caliber | Φ80mm | Φ130mm |
| Optional opening pressure | 35 / 55 / 85 kPa | 55 / 70 / 85 / 100 / 138 kPa |
| Opening pressure limit deviation | ±5 kPa | ±5 kPa (±10 kPa for 138 kPa) |
| Closing pressure (55kPa opening gear) | 29.5 kPa | 29.5 kPa |
| Seal pressure (55kPa open gear) | 33 kPa | 33 kPa |
| Signal switch contact capacity (AC) | AC 250V / 3A (inductive, cosΦ=0.4) | AC 250V / 3A (inductive, cosΦ=0.4) |
| Signal switch contact capacity (DC) | DC 220V / 1.5A (resistive) | DC 220V / 1.5A (resistive) |
| Mounting flange outside diameter D1 | 170mm | 235mm |
| Flange bolt circle diameter D2 | 200mm | 260mm |
| Total height H1 | 170mm | 190mm |
| Housing Material | stainless steels | stainless steels |
| Ambient temperature range | -30℃～+50℃ | -30℃～+50℃ |
| Operating Temperature Range | -50℃ ~ +100℃ | -50℃ ~ +100℃ |
| relative humidity | ≤95% (+20°C) | ≤95% (+20°C) |
VI. What are the precautions for installation and use?
Correct installation and use of the pressure relief valve directly determines whether it can act reliably at critical moments. The following are a few important installation and use points.
mounting position
The pressure relief valve should be installed on the top of the transformer tank cover, and if necessary, it can also be installed at an angle (the angle of inclination of 0 ° ~ 90 ° can be). When installing the pressure relief valve, it is necessary to configure the mounting flange (provided by the user), and the flange size should correspond to the size of the mounting holes in the product specification table. The installation height H must meet the requirements of the correspondence between the sealing pressure and the installation position to ensure that the valve does not open by mistake during normal operation.
Use of locking devices
Pressure relief valves with locking device (type with "B") can lock the locking device tightly during the oil pressure test of the transformer tank, preventing the valve from malfunctioning triggered by the test pressure.After the oil pressure test is completed, be sure to remove the locking device before putting it into operation., restore the normal working condition of the valve and ensure its reliable alarm action. This is the operation and maintenance of the most easily ignored, but also the most likely to lead to serious consequences of the operation of the link.
Post-action handling
After the pressure relief valve is operated, the valve will be closed automatically, but the mechanical signaling lever (J function) and electrical signaling switch (K function) will not be reset automatically, and need to be reset manually by O&M personnel on site. Before resetting, the cause of action should be identified and internal faults should be eliminated before resuming operation, and it should not be reset and put into operation directly without identifying the cause.
Configuration of Directional Injection Catheter
For products with directional spraying function (D type), an external flange and conduit can be welded at the outlet of directional spraying to introduce the released oil into the oil collecting tank. The installation direction of the conduit and the setting of the oil collecting tank should be planned uniformly before installation to ensure that the oil can be channeled smoothly to avoid oil accumulation and fire hazards.
The product must not be disassembled
The pressure relief valve has been calibrated before leaving the factory, and all parameters have been adjusted and qualified. Users are not allowed to disassemble the internal mechanism or adjust the opening pressure by themselves, otherwise it will destroy the factory calibration value and affect the protection precision and reliability of the product. If it is necessary to repair or re-calibrate, the manufacturer should be contacted.
Seven, the pressure relief valve action should be how to troubleshoot?
Once the pressure relief valve is actuated, it indicates that there has been a pressure abnormality inside the transformer, which must be taken seriously and not reset hastily. The following is the standardized troubleshooting process:
Step 1: Immediate blackout and isolation
After the pressure relief valve has been actuated, the transformer should be immediately isolated from the system and shut down to prevent the internal fault from continuing to expand while energized.
Step 2: Check the appearance
Check the appearance of the transformer tank whether there is deformation, leakage or burnt traces; check whether there is a large amount of oil spattering around the oil injection port, estimate the amount of oil sprayed how much to judge the initial degree of failure.
Step 3: Take an oil sample for testing
An oil sample is taken from the transformer drain valve and sent for dissolved gas analysis (DGA) to determine the type of internal fault based on the gas components. Abnormally high levels of acetylene (C₂H₂) usually mean that an arc discharge has occurred internally and is the most serious signal of a fault.
Step 4: Insulation Test
Perform insulation resistance measurements and DC resistance measurements on each side of the transformer windings to troubleshoot the presence of winding short circuits or grounding faults.
Step 5: Synthesizing Judgments
Combined with the appearance of the inspection, oil samples and electrical test results of a comprehensive judgment: if the slight pressure fluctuations caused by false operation (such as external short-circuit impact), after confirming that there is no internal damage can be manually reset and put into operation; if there is an obvious internal failure, it is necessary to arrange for the return to the factory for maintenance or replacement, and can not be forced to put into operation.
Why choose Inotera YSF series pressure relief valve?
YSF series pressure relief valves of Innotongda hold utility model patents, covering Φ25mm, Φ50mm, Φ80mm, Φ130mm caliber series, with models ranging from YSF4, YSF8, YSF9, YSF11, YSF16, etc., with flexible function combinations, and are suitable for various types of oil-immersed power equipment such as box-type substations, hermetically-sealed distribution transformers, large-sized main transformers, on-load tap-changers and so on. oil-immersed power equipment.
Safe and reliable structure, excellent three-proof performance
YSF series adopts stainless steel shell and built-in design of electrical switch, which effectively prevents accidental bump damage and false alarm caused by rain and fog. Junction box built-in terminals, wiring is convenient and safe, the junction box can also be connected to the external wire protection sleeve, comprehensive protection performance, three-proof (moisture-proof, mildew-proof, anti-salt spray) performance, suitable for outdoor and coastal and other harsh environments such as long-term operation.
Rich functional configuration, supports dual electrical signals
Φ80mm and Φ130mm caliber products can be configured with two sets of independent electrical alarm signal switches (SK type), the two signals are led out independently, one way to access the relay protection device, the other way to access the computer management system, without interfering with each other, to meet the requirements of the modern intelligent substation on the dualization of protection signals.
Full range of models, support customization
Innotransformer provides a complete series of models from Φ25mm for small-diameter box transformer to Φ130mm for large main transformer, and the functions of directional oil spraying, mechanical signaling, humid-heat belt version, and locking device can be configured according to requirements. If you have special installation size or function requirements, support customized development, welcome to provide transformer nameplate parameters contact selection.
statement denying or limiting responsibility
The content of this article is for general reference only, aims to introduce the working principle of the transformer pressure relief valve, model analysis and selection points, does not constitute the only basis for any engineering implementation or procurement decisions. The technical parameters involved in this article to the official product page information of InnoTech shall prevail, the actual specifications may vary due to product design version or customization requirements. The installation, commissioning and maintenance of the pressure relief valve must be carried out by qualified professionals, and the accompanying instructions and relevant standards shall prevail. The author and publisher of this article shall not be liable for any direct or indirect loss arising from reference to the contents of this article.
