Grid Connection Options - Double Feed

There is an increasing demand for connection of renewable energy parks to existing power systems infrastructure. .  However some options may still provide increased flexibility and increased availability and maintainability if considered as below.

H Connection ~ 1 x 1.5 CB Diameter

This is a fairly typical arrangement nominally allowing the feeds to be connected to the connection points independently or in tandem.

However it is to note that if the centre CB is out of service for any reason, the feeds must be operated independently with the consequential risk that a fault on one of the connection points (e.g. a cable fault to the right) would prevent that side connecting.

4-CB Ring Bus as Partial 2 x 1.5 CB Diameter

Whilst two feeds can be connected to two lines using three CBs as above, the addition of a fourth CB provides enhanced operational flexibility.

In a minimum operational arrangement only two CBs need to be closed for independent connection to the two connection points.

However for any reason, the feeds can still be connected to any connection point even with one CB out of service for maintenance.

This can easily be further augmented to full 1.5 CB populated diameters that would facilitate addition of a third (or more) 1.5 CB diameters for additional connection points

(The similarity of the bus layout here for two CBs in each diameter to the 3-CB Mesh connection of a single feed should be noted as a path for augmentation from single feed to double feed connections.)

Mesh or Full Ring Bus (as 2 x 1.5 CB Diameters)

This arrangement provides a variation of providing future expansion as a full ring bus arrangement.  The substation is laid out as 2 x 1.5 CB Diameters with "bus connected" transformers. Initial expansion is by adding the indicated equipment and yet further expansion is achieved with additional 1.5 CB Diameters as per the previous system, or making the ring bigger.

An issue for the expansion of this arrangement is the number TF Differential CT inputs available on the relay - the CTs cannot be paralleled as through currents between the CTs may cause one CT to saturate which would be seen as a false differential current causing TF Diff operation.  The solution to this is to rearrange into a traditional 1.5 CB arrangement or a traditional ring bus connecting all feeds.