RET670为二绕组和三绕组变压器，自耦变压器，升压变压器和发电机变压器块单元，移相变压器，特种铁路变压器和并联电抗器提供快速和选择性保护，监测和控制。IED被设计为在很宽的频率范围内正确工作，以适应电力系统在干扰和发电机启动和关闭期间的频率变化。
RET670具有快速、低阻抗差动保护功能，对ct的要求非常低。它适用于具有多达六个约束CT输入的多断路器安排的差分应用。差动保护功能具有二次谐波和波形块约束功能，以避免CT饱和和变压器涌流跳闸，并具有五次谐波约束功能，以避免变压器过励磁跳闸。
差分功能通过使用基于幅度测量和负序分量方向比较的灵敏差分保护功能，为低电平内部故障提供了高灵敏度。
多种低阻抗限制接地故障保护功能，作为灵敏、快速的绕组接地故障主保护。该功能包括一个内部/外部故障鉴别器，以增加安全性。
此外，还具有高阻抗差动保护功能。它可用于不同的应用，包括绕组保护、自耦变压器差动保护、并联电抗器保护、t馈线保护、母线保护和发电机差动保护等限制接地故障保护。
减压、布赫兹和温度装置的跳闸和报警信号可通过二进制输入通道直接发送到RET670，用于报警和备份目的。二进制输入高度稳定，防止干扰，以防止错误的操作，例如，直流系统电容放电或直流接地故障。

RET670 1MRK004816-AC

RET670 provides fast and selective protection, monitoring and control for two- and three-winding transformers, autotransformers, step-up transformers and generatortransformer block units, phase shifting transformers, special railway transformers and shunt reactors. The IED is designed to operate correctly over a wide frequency range in order to accommodate power system frequency variations during disturbances and generator start-up and shut-down.
RET670 has a fast, low-impedance differential protection function with very low requirements on the CTs.It is suitable for differential applications with multi-breaker arrangements with up to six restraint CT inputs. The differential protection function is provided with a 2nd harmonic and waveform-block restraint feature to avoid tripping for CT saturation and transformer inrush current, and 5th harmonic restraint to avoid tripping for transformer overexcitation.
The differential function offers a high sensitivity for low-level internal faults by using a sensitive differential protection feature based on an amplitude measurement and directional comparison of the negative sequence components.
Multiple low impedance restricted earth-fault protection functions are available as a sensitive and fast main protection against winding earth faults. This function includes a internal/ external fault discriminator for additional security.
Additionally, a high impedance differential protection function is available. It can be used for different applications including restricted earth fault protection as winding protection, autotransformer differential protection, shunt reactor protection, T-feeder protection, busbar protection and generator differential protection.
Tripping and alarm signals from pressure relief, Buchholz and temperature devices can be sent directly to RET670 via binary input channels for alarm and back-up purposes. The binary inputs are highly stabilized against disturbances to prevent incorrect operation due to, for example, DC system capacitive discharges or DC earth faults.