A criação de uma nova era na tecnologia de transformadores corresponde à criação de uma plataforma de três camadas para a modernização tecnológica da produção. Primeiramente, a inovação de componentes, como o desenvolvimento de núcleos amorfos, óleos ester e materiais de enrolamento de alta pureza, permite a redução de perdas e amplia as opções de instalação. Em segundo lugar, a inovação de sistemas, ou seja, monitoramento, gêmeos digitais e análises preditivas, transforma ativos em fontes de dados e diminui as interrupções forçadas em 30 a 50 %. Por último, a inovação de modelos de negócios, como aquisição de desempenho e transformador como serviço, permite a mudança da propriedade de risco e capital. A contínua revolução tripla transforma a aquisição de transformadores de uma simples compra em um processo de tomada de decisão estratégica orientado por dados.
A atualização da eficiência para a classe 1 da IEC 60076-20 permite a redução de perdas de 30 a 50%, resultando em retorno sobre o investimento em 4 a 9 anos.
O investimento em monitoramento garante o retorno mais rápido sobre o investimento para ativos críticos, muitas vezes proporcionando um retorno já após o primeiro incidente evitado.
Modelos de serviço permitem a liberação de capital e a transferência de risco, o que é especialmente importante para fins de fluxo de caixa.
Você deve adquirir transformadores com garantias de confiabilidade, documentação digital e testes sob supervisão.
Jiangsu Subian Electric Power é o produtor de transformadores modernos e transformadores prontos para soluções de monitoramento de atualização a preços acessíveis.
O que é um Mudador de Tap do Transformador?
A mudador de tap é um dispositivo de comutação anexado a um enrolamento de transformador em vários pontos de derivação. Com a ajuda do dispositivo, é possível alternar a conexão entre diferentes taps que resultam em mudanças na quantidade de voltas do enrolamento e, assim, variações na tensão do lado secundário. Assim, o mudador de tap é, de fato, o mecanismo de ajuste de tensão incorporado dentro do tanque do transformador ou montado sobre o enrolamento.
A tensão experimentada por várias redes sofre constantes reduções e aumentos devido a cargas que variam durante o dia, queda da linha de energia, mudanças na tensão fornecida pela rede. A saída de tensão fixa de um transformador em uma razão obtida durante a produção pode levar a problemas com o fornecimento de tensão e o mudador de tap fornece os meios confiáveis de correção.
Existem três aspectos críticos usados para caracterizar qualquer tipo de mudadores de tap: seu passo de tensão (expresso como porcentagem da tensão nominal), seu número de posições e a faixa da tensão regulada. Por exemplo, pode haver um transformador de distribuição que tem a capacidade de funcionar em uma faixa de ±2×2.5%, pois possui 4 posições de tap, enquanto transformadores maiores são fornecidos com mudadores de tap mais avançados.
Mudadores de Tap Off-Circuito vs. On-Load
| Característica | Mudador de Tap Off-Circuito (OCTC) | Mudador de Tap On-Load (OLTC) |
|---|---|---|
| Condição de operação | Transformador desenergizado | Transformador carregando carga |
| Faixa típica | ±2×2.5% (5 posições), ±4×2.5% (9) | ±8×1.25% (17 posições) e mais amplo |
| Mecanismo | Manual, interruptor mecânico simples | Acionamento por motor, desvio com mola, transição a vácuo ou resistor |
| Impacto de custo no transformador | +2 a +5% | +10 a +30% |
| Manutenção | Mínima | Regular; filtração de óleo e inspeção de contatos |
| Melhor para | Distribuição, carga estável, ajuste sazonal | Transformadores de potência, carga flutuante, controle automático de tensão |
A escolha entre as duas opções é baseada em um aspecto chave: é necessário fazer algum ajuste na tensão produzida pelo transformador quando está em operação? Transformadores de distribuição que atendem cargas estáveis podem ser ajustados sazonalmente usando um OCTC e, portanto, não incorrer em quase nenhum custo. No entanto, transformadores de potência que fornecem cargas flutuantes devem ser equipados com um OLTC para garantir a qualidade da tensão fornecida e, portanto, suportar um custo adicional de 10-30% para conformidade com os requisitos relativos à qualidade da tensão.
Como funciona um Mudador de Tap sob Carga
Não é fácil mudar taps sob carga. Você não pode simplesmente abrir o circuito no ponto de tap porque isso interromperia a corrente de carga e resultaria em um arco que danificaria os contatos. O OLTC oferece uma solução em duas etapas envolvendo um seletor que permite escolher a nova posição do tap sem que a corrente seja ligada e um interruptor de desvio que move a carga de corrente no tap atual para a nova posição. A transição é fornecida pela impedância de transição. Isso pode ser um elemento resistivo ou um interruptor a vácuo. Assim, a corrente flui continuamente e é extinta imediatamente.
No OLTC do tipo resistor, o desvio faz
a carga de corrente passar por um elemento resistivo ou dois ao mudar os taps. No caso de um design do tipo vácuo, é o interruptor a vácuo que cuida da extinção do arco, mantendo assim o óleo mais limpo e estendendo o tempo entre manutenções. Ambos os tipos são baseados nos requisitos de desempenho da IEC 60214-1 e nas especificações de aplicação da IEC 60214-2, e a escolha entre eles é determinada principalmente pelos cálculos de custo do ciclo de vida, uma vez que os OLTCs a vácuo são mais caros para instalar, mas requerem menos manutenção.
Tipos de Mudadores de Tap
| Tipo | Princípio de Operação | Faixa Típica de Classificação | Faixa de Preço |
|---|---|---|---|
| Mudador de tap fora de circuito (manual) | Interruptor mecânico, sem carga | Até 10 MVA típico | $200-$1,500 |
| OLTC do tipo resistor (tipo tanque ou cabeça) | Desvio com resistores de transição | Até ~60 MVA | $3,000-$18,000 |
| OLTC do tipo vácuo | Interruptor a vácuo no desvio | Até 200+ MVA | $5,000-$30,000 |
| OLTC do tipo reator | Reactor transition, older designs | Large power transformers | Rare; replaced by resistor/vacuum |
| Motor drive unit (accessory) | Remote/auto operation of any OLTC | — | $2,000-$10,000 |
For most applications that we deal with today, the issue comes down to whether one chooses a resistor or a vacuum OLTC, although recently, the latter has become more popular and is usually employed in new power transformers because of the longer periods of maintenance. Off-circuit changers, on the other hand, are a completely different product type, simpler and quite inexpensive ($200-$1500), located inside distribution tanks and regulated few times a year when a transformer is switched off.
Key Ratings and Specifications
| Parâmetro | Significado | Valores Típicos |
|---|---|---|
| Corrente nominal | Maximum continuous load current the OLTC can carry | 250-1,250 A |
| Tensão de passo nominal | Voltage across the tap range | Up to 3,300 V per step in large units |
| Frequência nominal | Must match the system (50 or 60 Hz) | 50 Hz / 60 Hz |
| Number of positions | Total selectable taps | 5, 9, 17, 33 |
| Step voltage (%) | Voltage change per step as % of rated | 1.25%, 2.5%, 5% |
| Padrão | Design and test basis | IEC 60214-1/-2, IEEE C57.131 |
There are two numbers that are typically out of order in purchase orders. These are the rated through-current, which must be greater than the maximum continuous current rating of the transformer (including overload ratings), and the step voltage — the high step voltage for a given current places quite different demands on the diverter than carrying the same current at a low step voltage and therefore the OLTC rating combines these two numbers.
To illustrate the subject, let’s bring in some guidelines on the tap changer parameters for the traditional types of transformers — the figures that you are supposed to mention in your RFQ:
| Classe de Transformador | Tap Changer Type | Typical Range | Through-Current | Approx. Price Impact on Transformer |
|---|---|---|---|---|
| 100-1,000 kVA distribution | Off-circuit (OCTC) | ±2×2.5% / ±4×2.5% | Up to 1,500 A | +2 to +4% |
| 1-10 MVA industrial | OLTC, resistor type | ±6×2.5% | 300-700 A | +10 to +18% |
| 10-60 MVA substation | OLTC, resistor or vacuum | ±8×1.25% | 400-1,250 A | +12 to +25% |
| Above 60 MVA power | OLTC, vacuum type | ±8×1.25% or wider | 1,250-2,500 A | +15 to +30% |
Tap Range, Steps, and Position Selection
Selecting the tap range is a voltage-regulation determination, as opposed to being an educated guess. The process goes generally as follows:
First step is measuring the voltage variation, by recording the primary-side voltage during a full load cycle. The primary voltage changes by ±5-10% from light loads to heavy loads.
Second step is to calculate the required regulation range. It is essential to add together impedance drop in the transformer, which is typically 4-8% when at full load, and voltage variation on the primary side to get to know regulations range.
Next step is to find out the step size used in establishments. Standard distribution step size varies according to each transformer used, which varies from 2.5% to 1.25% for power transformers needing more precision.
Fourth step is to pick out the midpoint of the range, which should be centered around a nominal ratio of ±8×1.25%, producing range of voltage regulation tapping by 10% for 33/11kV applications.
Final step is to synchronize with the AVR. When working on automatic mode, the relay keeps track of the voltage on the bus and sends the command to the motor drive to change each step in delay mode, which is approximately 30-120 seconds.
Where Each Type Belongs
- Distribution transformers (50-2,500 kVA): Off-circuit tap changers, ±2×2.5% or ±4×2.5%, adjusted at commissioning and seasonally;
Substation power transformers (5-60 MVA): Resistor-type OLTC with ±8×1.25% or ±6×2.5% adjustments with the possibility of automatically regulating voltage;
Large power and generator transformers (>60 MVA): Vacuum-type OLTC operating over wide ranges, sometimes on both HV and LV windings (two OLTCs);
Industrial furnace and arc loads: OLTCs made for fast operations and big switching rates;
Renewable energy tie transformers: OLTC to help with variable generation and hold voltage in the grid.
Comparação de Marcas e Preços
| Marca | Origem | Strength | Approx. Price Range (OLTC, standalone) |
|---|---|---|---|
| MR (Reinhausen) | Alemanha | The global OLTC benchmark; vacuum and resistor types | $6,000-$35,000 |
| ABB | Suíça/Suécia | Complete transformer + OLTC packages | $5,000-$30,000 |
| Siemens | Alemanha | OLTC for large power transformers | $6,000-$32,000 |
| Hitachi Energy | Suíça | Power transformer tap changing | $7,000-$35,000 |
| Schneider Electric | França | Distribution-class tap changers | $3,000-$15,000 |
| Jiangsu Subian Electric Power | China | OCTC and OLTC-equipped transformers, IEC 60214 coordination | $2,000-$12,000 |
In the field of on-load tap changers, MR Reinhausen is regarded as the benchmark as the majority of large transformers globally are manufactured by MR or its licensed version; ABB, Siemens, and Hitachi Energy providing complete solutions around these machines or their partner’s OLTC technology. The equipment passes all necessary tests according to IEC 60214 and IEEE C57.131, having all required records of its lifetime and maintenance. For those who want the same result but at a more attractive price, Jiangsu Subian Energia Elétrica creates equipment with the same OLTC able to make devices as one. Jiangsu Subian Electric Power supplies equipment successfully operating for IEC 60214 and shipping worldwide with all commonplace records of tests at a price 40-60% less than the cost of European transformers. If you opt for MR equipment or find a cost-efficient analogue, ensure that you mention OLTC’s name in your purchase agreeing to purchase the exact unit rather than just referring to it in general.
Step-by-Step Selection Guide
First, choose between an OCTC or an OLTC. If you can take the transformer out of service while changing taps and if the load changes gradually, then an OCTC is the way to go. If, however, you want to keep the voltage constant while the load is in a state of constant change, then you should choose an OLTC.
Next, define the regulating range. Take down the actual voltage variation and find the required range, keeping in mind that +8×1.25% is enough to cover most situations when using electricity.
Next, choose the step size; use 2.5% for economy purposes and 1.25% for more precise regulation.
Then, check the through-current. OLTC must have a capacity greater than the maximum continuous current of the transformer, which also includes any overload commitments.
Furthermore, ensure that the voltages are compatible. Confirm that the OLTC handles your transformer’s step voltage, because the product of the tap current by the step voltage will cause stress on the diverter.
Decide on whether you want to use a resistor or a vacuum. A resistor would be a better option as it is cheaper and has been in use for a long time, whereas a vacuum would have lower maintenance costs.
Finally, do not forget to include automatic controls. A motor drive, AVR relay, and position indicator are not only necessary for your OLTC, but you should also specify the control voltage needed for it to function.
Installation and Maintenance
The most maintenance-intensive aspect of a modern transformer is its use of on-load tap changers, as they are the only transformer components to perform mechanical work under load conditions. The switching oil used in typical resistor-type OLTC devices needs to be filtered or replaced according to the manufacturer’s schedule, usually after a period of 100,000 operations or 5-7 years, whichever comes first, while vacuum-operated OLTCs prolong the operating time considerably.
Maintenance procedures
1. Measure and draw up a monthly chart of the operating counter readings.
2. Take OLTC oil samples separately from the main tank oil. The diverter oil carbonizes under switching and gets deteriorated much quicker.
3. Inspect contacts for erosion during general overhauls, and take transition resistor readings according to the requirements of the manual.
4. Test torque characteristics of the motor drive and AVR-relay settings once a year.
5. Make sure that tap position indicator corresponds to the current winding position before any manual operation.
Perguntas Frequentes
How much does a tap changer add to transformer cost?
An off-circuit tap changer adds roughly 2-5% to the transformer price. An on-load tap changer adds 10-30%, because the OLTC itself costs $3,000-$30,000 (by rating) plus the motor drive and control system. For a 10 MVA transformer, budget $10,000-$25,000 for the OLTC increment.
What is the difference between an off-circuit and an on-load tap changer?
An off-circuit tap changer (OCTC) can only be operated when the transformer is de-energized; it is a simple, cheap switch used to match the transformer to its feeder’s average voltage profile. An on-load tap changer (OLTC) switches taps while the transformer carries load, using a diverter and transition impedance to avoid interrupting current, which makes it suitable for automatic voltage regulation under varying load.
What tap range do I need for my transformer?
For distribution transformers, ±2×2.5% (5 positions) or ±4×2.5% (9 positions) covers most cases. For power transformers feeding fluctuating loads, ±8×1.25% (17 positions) is the common choice, giving ±10% total range. The correct value comes from measuring your voltage variation and transformer impedance drop — do not pick a range from a catalog.
How often should an on-load tap changer be maintained?
Resistor-type OLTCs typically need oil filtration or replacement every 100,000 operations or 5-7 years, whichever comes first. Vacuum-type designs extend that to roughly 300,000 operations. Monitor the operation counter, sample the OLTC oil separately from the main oil, and inspect contacts at each major overhaul.
Can I retrofit an OLTC onto a transformer designed for off-circuit operation?
Infrequently, and typically not cheap. The winding should have the proper tap configuration, the tank should have a mounting turret, and the cooling and clearances must work for the diverter. It is nearly always cheaper to specify the OLTC at the design stage or buy a new transformer. If the need for voltage regulation exists for an already installed fixed-tap unit, one should think about a separate voltage-regulating transformer instead.
Referências
- IEC 60214-1 — Tap-Changers, Performance Requirements and Test Methods — The core standard for tap changer design and testing.
- IEC 60214-2 — Tap-Changers, Application Guide — Guidance on selecting ranges, steps, and ratings.
- IEEE C57.131 — Requirements for Load Tap Changers — North American OLTC standard.
- MR Reinhausen — Tap Changer Portal — The leading OLTC manufacturer’s product and application documentation.
- IEC 60076-1 — Power Transformers, General Requirements — Transformer-level standards that the tap changer must satisfy as part of the unit.
- ABB Transformers — Reference for transformer and tap changer integration.
Conclusão
enrolamento mudador de tap selection can be considered a voltage-regulation solution masquerading as a selection of components. It is necessary to evaluate the test results relative to voltage variation and transformer impedance decrease beforehand. The next step is to select the tap changer according to the proper voltage range and tap size, then select a corresponding model to meet its requirements and specifications, including selection of an off-load tap changer if applicable.
An OCTC adds to the cost of the transformer only roughly 2% to 5%, whereas an OLTC increases the cost in the amount of approximately 10% to 30%. The current and voltage should be matched according to the operating conditions, instead of naming the brand of the equipment.
For off-circuit and on-load tap changer equipped transformers built to IEC 60214 and IEC 60076, contact Jiangsu Subian Electric Power decidem www.subian-electric.com with your voltage profile and load data for a specification and quote.