Goals and Symptoms

Summary

SEL 2030 devices are used to communicate with Schweitzer Engineering Laboratories (SEL) relays. The relays only communicate with SEL proprietary protocol. The 2030 can convert this to Modbus for the use of PRODUCTS such as ION Enterprise 5.0.
We use the name SEL 2030 but this article also applies to other modules in this product family including the SEL 2020 and SEL 2032.

ION Enterprise 5.0 is configured to translate the Modbus data into the ION network. Within this network a Virtual ION Processor (VIP) can be used to perform logical actions based on the information obtained from the relay.

One common action is to detect a change in state of a Boolean value. A series of VIP Setpoint modules can be configured to monitor the state of each value.  When the state changes the VIP Setpoint module records an event but can also be used to trigger an action.

Symptoms

The VIP Setpoint module shows repeated events without an actual change in the relay state.  This may always appear as an OFF event.

Causes and Fixes

Cause

The ION Enterprise Modbus master repeatedly asks the SEL 2030 for updates.  If the SEL 2030 is providing the data directly from the port to which the relay is attached (as opposed to the port the master is attached to) then the SEL 2030 will randomly reply with Modbus exceptions. These happen when the incoming request happens at the same time as the relay is updating its information in the SEL 2030.

These Modbus exceptions may cause a VIP Setpoint module to incorrectly register an event.

Workaround

There are two ways to work around this problem.

On newer SEL 2030 devices the master port can be configured to not send exceptions when it is busy. In the port set-up configure the "BUSY_DIS" setting to "Yes" from the default "No"

On all SEL 2030 devices you can use Memory Move commands to re-map the individual relay's data into the memory used by the Modbus master