This is because the authority of outlet PowerDissipation is read-only, not read-write, so you cannot use SNMP to delete power Dissipation.There is another solution by using HTTP API for customers to delete aggregate power dissipation Please use the below link to do that. 

https://PDU_IP/api/clearPD?usr=USERNAME&pwd=PASSWORD&type=TYPE&index=INDEX 

For USERNAME and PASSWORD, please type the ID/PWD of administrator. For TYPE, we can choose all, bank and outlet For INDEX, we can assign which bank or which outlet. Below is an example.

https://192.168.0.60/api/clearPD?usr=administrator&pwd=password&type=outlet&index=1